443

25. DITRICHACEAE Limpricht

Rodney D. Seppelt

Plants minute or rather small to medium-sized, gregarious or loosely to densely tufted. Stemserect, simple or forked, with a central strand. Leaves mostly lanceolate, acuminate or subulate,straight or somewhat curved, rarely sheathing at base; in numerous rows (2 rows in Distichium);costa single, well developed, subpercurrent to excurrent, in section with 1 row of guide cellsand 2 stereid bands, adaxial band sometimes much reduced; lamina cells smooth (± roughenedin subula in Distichium); basal cells elongate, narrower towards the margins, those of basalangles not differentiated or forming a marginal border; distal cells isodiametric or short-rectangular to elongate, walls firm. Specialized asexual reproduction occasional, as multicellularfilamentous gemmae borne in axils or along stems, or as specialised tubers or filamentouspropagules on rhizoids. Sexual condition dioicous, autoicous, paroicous, or synoicous; perigoniaaxillary or on short branches adjacent to perichaetia, or terminal on separate plants; perichaetialleaves not markedly differentiated or with a longer, broader sheathing base and shorter subulateapex. Seta short to ± elongate, yellow to orange, reddish brown, brown, or reddish purple;capsules immersed to emergent and subglobose to long-exserted and ± cylindric, erect to inclinedor pendulous, often ± curved or asymmetric; cleistocarpous, gymnostomous, or peristomate;annulus, when present, usually of 2–3 rows of larger cells, deciduous; peristome, when present,single, of 16 teeth, variously split into two terete filaments or perforate to near the base;operculum conic to short-rostrate. Calyptra cucullate, rarely mitrate. Spores spheric to ovoidor ± reniform, finely to coarsely papillose, verrucose, or somewhat vermicular or reticulate.

Genera 25, species ca. 140 (9 genera, 25 species in the flora): cosmopolitan, greatest occurrencein temperate regions.

Species of Ditrichaceae usually colonize soil, rarely wood, and some species have a distinctpreference for calcareous substrates. The family is poorly defined and separated fromDicranaceae primarily on peristome characteristics, with the teeth divided into terete rather thanflat filaments, and the general absence of vertical pit-striations. In some species, however, obliqueornamentation is present, at least in the distal portion of the teeth. W. R. Buck and B. Goffinet(2000) included 25 genera, with one hybrid genus, Pleuriditrichum, in the family. The inclusionof at least some of the genera seems somewhat anomalous. Within the flora, Ceratodon,Distichium, Ditrichum, Saelania, and Trichodon are peristomate, while Cleistocarpidium,

rzanderText BoxFlora of North America, Volume 27, 2007

444 DITRICHACEAE

Eccremidium, Pleuridium, and Pseudephemerum are cleistocarpic. Although in this treatmentit is included in Ditrichaceae, Pseudephemerum was placed in Dicranaceae by Buck and Goffinet.

SELECTED REFERENCE Britton, E. G. 1913b. Ditrichaceae. In: N. L. Britton et al., eds. 1905+. North American Flora.... 47+vols. New York. Vol. 15, pp. 55–67.

1. Leaves in two rows, base ± sheathing, abruptly narrowed to a ± roughened subula. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2. Distichium, p. 448

1. Leaves in more than two rows.2. Leaves glaucous blue-green . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4. Saelania, p. 4582. Leaves yellow-green to green or brownish green, never glaucous blue-green.

3. Leaves squarrose from a sheathing base, subulate, the subula tubulose and stronglyprorulose abaxially . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5. Trichodon, p. 459

3. Leaves lanceolate to subulate, the base ± sheathing or not, not squarrose.4. Stems generally elongate, 0.5–4 cm or sometimes longer; capsule, when present,

peristomate.5. Leaves lanceolate, ovate-lanceolate or triangular-ovate to obovate, margins

recurved; seta reddish purple to yellowish orange, capsule erect to inclined,strongly sulcate when dry . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1. Ceratodon, p. 445

5. Leaves lanceolate to subulate, margins mostly plane, occasionally weaklyrecurved; seta pale yellow to yellow to orange to reddish brown, capsuleerect to suberect, not sulcate when dry . . . . . . . . . . . . . . . . . . . . . . . . 3. Ditrichum, p. 450

4. Stems generally very short, 0.2–0.8 cm; capsule, when present, immersed andcleistocarpic.6. Leaves loosely erect, subulate-acuminate from a lanceolate base, margins

sharply serrate distal to the shoulders, costa excurrent, filling subula;seta stout, arcuate; capsule laterally emergent, pendulous . . . . . . . . 7. Eccremidium, p. 461

6. Leaves erect-spreading or appressed or reflexed-recurved, oblong tolanceolate or subulate, margins plane, serrulate towards apex, costasubpercurrent to excurrent; seta short, erect to curved, not arcuate; capsuleerect to inclined, not pendulous.7. Leaves reflexed-recurved, lanceolate from an ovate base, margins plane,

entire, serrulate at the flat apex; laminal cells thin-walled, proximalcells larger, rectangular, distal cells rhombic; capsule ovoid . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9. Pseudephemerum, p. 467

7. Leaves erect-spreading or appressed, oblong to lanceolate with subulateto acuminate tips, margins plane, entire to serrate or abruptly toothed;lamina cells quadrate-rectangular proximally, becoming irregularlyrhomboid to trapezoidal and elongated distally; capsule ovoid to elliptic.8. Stem leaves 2–4 mm, loosely erect, subulate from an ovate-

lanceolate to narrowly obovate base, entire, serrulate along subula;capsule immersed, ovoid, broadest at base, whitish, spore sac orange. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6. Cleistocarpidium, p. 460

8. Stems leaves 0.5–2 mm, erect-spreading or appressed, imbricate tospreading, oblong to lanceolate with subulate to acuminate tips,entire to serrate or abruptly toothed; capsule immersed, ovoid toelliptical, orange to brown . . . . . . . . . . . . . . . . . . . . . . . . . . . 8. Pleuridium, p. 463

DITRICHACEAE 445·1. CERATODON Bridel, Bryol. Univ. 1: 480. 1826 · [Greek keratos, horn, and odon,

tooth, alluding to peristome teeth forked like goat horns]

Terry T. McIntosh

Plants in loose to dense tufts, turfs, or mats, green to dark green, brownish green, light green,or yellow-green, often tinged reddish brown or purple. Stems (0.2–)1–3(–4) cm, often branched;rhizoids at base, papillose. Leaves erect-patent, contorted or somewhat crisped, rarely straightwhen dry, lanceolate, ovate-lanceolate, or triangular-lanceolate, or elliptical to ovate andsomewhat concave, margins recurved to near apex, rarely plane, irregularly serrate or smoothdistally; costa sub-percurrent to excurrent, sometimes as a long, smooth awn, 1 row of guidecells, two stereid bands, hydroid cells present between guide cells and abaxial stereids; mediallaminal cells of somewhat uneven shape and size across leaf, more or less quadrate or short-rectangular, often irregularly angled or rarely rounded, non-pitted. Specialized asexualreproduction absent or as multicellular filamentous propagules with thin walls scattered alongthe stems or occasionally as rhizome nodules. Sexual condition dioicous; male and female plantsabout the same size; perigonial leaves ovate, concave, short-acuminate or rarely long-acuminatein well-developed plants; perichaetial leaves convolute-sheathing, abruptly subulate to graduallyacuminate. Seta red, purplish, yellow, or yellow-orange, elongate, twisted when dry, erect.Capsule erect to inclined or horizontal, exserted, dark red to reddish or purplish brown, topale brown, pale yellow or yellow-orange, oblong-ovoid to oblong-cylindric or cylindric, oftensomewhat asymmetric and deeply furrowed, smooth to strongly sulcate when dry, usuallystrumose; annulus of 2–3 rows of large, deciduous, revoluble cells; operculum conic to long-conic, straight; peristome single, teeth 16, split nearly to their base into 2 filiform segments freeto united at their nodes basally, 5–18 articulations, basal membrane present, finely papillose tospinulose-papillose. Calyptra cucullate. Spores globose, smooth to finely papillose.

Species 3 (2 in the flora): worldwide.Historically, Ceratodon has been a troubling genus. Taxonomic interpretations, especially with

respect to C. purpureus in the broad sense, have varied widely, mainly because of the high degreeof environmental and suspected genetic variation across its range. J. S. Burley andN. M. Pritchard (1990) provided the most thorough treatment of Ceratodon to date, reducingthe number of species to four and subspecies of C. purpureus to three. One of their species, C.conicus, is treated here as a subspecies of C. purpureus, based on the apparent gradation andreduction of all of the characters that they used in their treatment. However, there remains agreat need for a detailed study of this genus within North America.

SELECTED REFERENCES Burley, J. S. and N. M. Pritchard. 1990. Revision of the genus Ceratodon (Bryophyta). Harvard Pap.Bot. 2: 17–76. Snider, J. A. 1994. Ceratodon. In: A. J. Sharp, et al., eds. The moss flora of Mexico. Mem. New York Bot.Gard. 69: 103.

1. Vegetative leaves elliptic to ovate-lanceolate, concave, obtuse; distal laminal cells usually12–16 mm, sometimes longer; leaf margins plane to weakly recurved and usually entire;most costa sub-percurrent; capsule ovate to ovate-cylindrical, about 1 mm; sporesusually19–21 µm; restricted to Arctic regions . . . . . . . . . . . . . . . . . . . . . . . . . . . 1. Ceratodon heterophyllus

1. Vegetative leaves usually lanceolate to ovate-lanceolate, acute to short-acuminate; distallaminal cells usually 8–12 mm; leaf margins recurved and usually toothed distally; costapercurrent to long-excurrent; capsule ovate-cylindrical to cylindrical, usually longer, to3 mm; spores usually 11–14 µm; widespread . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2. Ceratodon purpureus

Ceratodon

446 DITRICHACEAE

1. Ceratodon heterophyllus Kindberg, OttawaNaturalist 5: 179. 1892

Ceratodon purpureus var.obtusifolius Limpricht; C. purpureusvar. rotundifolius Berggren

Plants in dense tufts or mats, greento dark green to brownish green.Stems 0.3–1 cm. Leaves looselyimbricate, somewhat contortedwhen dry, ovate to ovate-lanceolate, concave and often

somewhat cucullate, (0.35–)0.5–0.9(–1.5) mm, marginsplane to weakly recurved, often only at mid-leaf, andentire to, rarely, weakly toothed distally, apices obtuse;most costae ending before apex; medial laminal cells(9–)12–16(–22) µm, thin-walled to somewhat thickened.Seta (0.9–)1.5(–2.5) cm, red. Capsule ovate-cylindric to,occasionally, ovate, (0.9–)1–1.2(–1.5) mm, stronglysulcate when dry; peristome segments free at their nodes,finely papillose, dark red with pale borders to, rarely,completely pale. Spores (18–)19–21(–22) µm.

Capsules mature early summer–late fall. Sandy,usually moist soil, Arctic habitats; low elevations(0–200 m); Greenland; N.W.T., Yukon; Alaska; Eurasia.

In Northwest Territories, Ceratodon heterophyllus isfound only on Prince Patrick Island.

Ceratodon heterophyllus has also been treated asC. purpureus forma heterophyllus (Kindberg) Britton,and R. R. Ireland (1980) considered it to be a variety ofC. purpureus, but J. S. Burley and N. M. Pritchard (1990)provided ample evidence that it is a distinct species. Thebroadly ovate leaves of C. heterophyllus grade into somealpine variations of C. purpureus.

SELECTED REFERENCE Ireland, R. R. 1980. The taxonomic status ofCeratodon heterophyllus. Bryologist 83: 234–237.

2. Ceratodon purpureus (Hedwig) Bridel, Bryol. Univ.1:480. 1826

Dicranum purpureum Hedwig, Sp.Musc. Frond., 136, plate 36. 1801;Ceratodon purpurascens (Hedwig)Jennings; C. purpureus var.purpurascens (Hedwig) Bridel; C.purpureus var. xanthopus Sullivant

Plants in open to dense tufts, turfs,or mats, green, dark green,brownish green, light green or

yellow-green, usually darker proximally, often tingedreddish brown or purple. Stems (0.2–)1–3(–4) cm.Leaves crowded, erect-patent to contorted or somewhatcrisped, rarely straight when dry, lanceolate, ovate-

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DITRICHACEAE 447·lanceolate, or triangular-lanceolate, 0.35–2.8 mm,margins recurved to near apex or rarely plane, irregularlyserrate to uneven or smooth distally, apices acute to short-acuminate or, rarely, obtuse; costa strong, sub-percurrentto excurrent, sometimes as a long, smooth awn, mediallaminal cells (6.5–)8–12(–14) µm, cell walls even, usuallyof medium thickness, often somewhat thicker androunded at the cell angles. Seta 1–3(–4) cm, variousshades of red, orange, or yellow. Capsule oblong to long-cylindric, (1–)2–2.5(–3) mm, smooth to strongly sulcatewhen dry; free to united at their nodes, finely papilloseto spinulose-papillose, dark red and bordered tocompletely pale and absent borders. Spores (10–)11–14(–17) µm.

Subspecies 4 (3 in the flora): nearly worldwide.

1. Plants usually of various shades of green to red-brown; seta red to dark brown; capsule inclinedto horizontal, oblong to cylindric, strumose, deeplysulcate when dry, usually red to red-brown topurplish, occasionally light brown . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2a. Ceratodon purpureus

subsp. purpureus1. Plants pale green to yellow-green to yellowish

brown; seta pale yellow to yellow-orange, rarelyreddish; capsule slightly inclined to erect, narrowlycylindric to cylindric, not or weakly strumose,smooth to sulcate when dry, usually pale brown toyellow (golden) -orange.2. Stems usually less than 0.5 cm; distal leaves

relatively compact, straight to slightly twistedwhen dry, usually forming a comal tuft, slightlyspreading when wet, 0.6–1.2 mm, marginsoften entire; costa long-excurrent as a smoothawn on many leaves, awns sometimes as longas leaf blade . . . . . . . . . . . 2b. Ceratodon purpureus

subsp. conicus2. Stems usually greater than 1 cm; distal leaves

more open, usually crisped when dry, notforming a comal tuft, spreading when wet, 1.2–1.8 mm, margins often toothed; costapercurrent to slightly excurrent . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2c. Ceratodon purpureus

subsp. stenocarpus

2a. Ceratodon purpureus (Hedwig) Bridel subsp.purpureus

Dicranum purpurascens Hedwig

Plants in open to dense tufts, turfs,or mats, green, dark green, tobrownish green, rarely yellow-green. Stems (0.3–)0.6–1.4(–4) cm.Leaves erect-patent to contorted orsomewhat crisped when dry, rarelyforming a comal tuft, patent toerect-patent to spreading when

wet, 0.35–2.8 mm, distal margins usually toothed; costapercurrent to slightly excurrent. Seta usually red to dark

brown. Capsule usually inclined to horizontal, (0.8–)1.3–1.8(–3) mm, usually arcuate, red to red-brown to purplishto, occasionally, light brown, deeply sulcate when dry,usually strumose, occasionally light brown. Peristometeeth usually bordered, usually with 8–16 articulations.

Capsules mature early summer–late fall. Varioushabitats, but most common on open soil, also rock ledges,tree bases, roof tops, old wood, a common colonizer ofsoil following fires; low to high elevations; Greenland;Alta., B.C., Man., N.B., Nfld. and Labr., N.W.T., N.S.,Nunavut, Ont., P.E.I., Que., Sask., Yukon; Ala., Alaska,Ariz., Ark., Calif., Colo., Conn., Del., D.C., Fla., Ga.,Idaho, Ill., Ind., Iowa, Kans., Ky., La., Maine, Md., Mass.,Mich., Minn., Miss., Mo., Mont., Nebr., Nev., N.H., N.J.,N.Mex., N.Y., N.C., N.Dak., Ohio, Okla., Oreg., Pa.,R.I., S.C., S.Dak., Tenn., Tex., Utah, Vt., Va., Wash.,W.Va., Wis., Wyo.; Mexico; Eurasia; Pacific Islands(Hawaii).

2b. Ceratodon purpureus subsp. conicus (Hampe)Dixon, Stud. Handb. Brit. Mosses, 68. 1896

Trichostomum conicum Hampe inMüller Hal., Syn. Musc. Frond. 1:575. 1849; Ceratodon conicus(Hampe) Lindberg

Plants in compact mats, usuallyyellow-green. Stems (0.2–)0.3–0.6(–3) cm. Leaves straight toslightly twisted when dry, usuallyforming a comal tuft, slightly

spreading when wet, 0.6–1.2 mm, margins often entire;costae long-excurrent as a smooth awn on many leaves,awns sometimes as long as leaf blade. Seta yellow toyellow-orange. Capsule usually slightly inclined to erect,usually straight, (0.8–)1–1.8(–2.2) mm, pale brown toyellow (golden) orange, smooth to sulcate when dry,usually weakly strumose. Peristome teeth faintly borderedto unbordered, usually with 5–9 articulations.

Capsules mature early summer–late fall. Common oncalcium-rich soils of arid habitats; moderate elevations(300–800 m); B.C.; Idaho, Minn., Oreg., Wash.; Eurasia;n Africa; Atlantic Islands (Canary Islands).

Subspecies conicus is apparently widespread in somearid regions of western North America. J. S. Burley andN. M. Pritchard (1990) considered its status in NorthAmerica to be uncertain. However, fertile collections,although uncommon, fit well within their concept. Itappears to be widespread in the semi-arid steppe regionsof central Washington and adjacent British Columbia.In these arid habitats, it is often admixed with other low-growing species (e.g., Bryum spp. and Didymodon spp.)as part of the biological crust community.

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448 DITRICHACEAE

2c. Ceratodon purpureus subsp. stenocarpus (Bruch& Schimper) Dixon, Bull. New Zealand Inst. 3: 50.1914

Ceratodon stenocarpus Bruch &Schimper, Bryol. Europ. 2: 146.1846

Plants usually in open turfs andmats, usually yellow-green. Stems(0.3–)0.6–1.4(–4) cm. Leaveserect-patent to contorted orsomewhat crisped when dry, rarelyforming a comal tuft, patent to

erect-patent to spreading when wet, 0.35–2.8 mm, distalmargins usually toothed; costae percurrent to slightlyexcurrent. Seta pale yellow to yellow-orange. Capsule

slightly inclined to erect, usually arcuate, (1–)1.7–2.3(–3.7) mm, pale brown to yellow (golden) orange, smoothto sulcate when dry, weakly strumose to struma absent.Peristome teeth usually bordered, usually with 8–16articulations.

Capsules mature early summer–late fall. Soil, treebases, rock ledges, often on burned ground; low to highelevations; Ariz., Calif., N.Mex., Tex.; Mexico; WestIndies; Central America; n South America; Eurasia;Africa.

J. S. Burley and N. M. Pritchard (1990) noted thatsubsp. stenocarpus is mainly tropical to sub-tropical, andfrequently at higher elevations within these regions, butalso note its distribution in southwestern North America.

2. DISTICHIUM Bruch & Schimper, Bryol. Europ. 2: 153. 1846 · [Greek distichos, intwo rows, alluding to leaves]

Rodney D. Seppelt

Plants slender, elongate, in dense tomentose tufts, yellowish green to dark green. Stems 1–6cm, simple or branched; rhizoids from base to middle of stem forming a conspicuous tomentum.Leaves distichous, linear subula spreading from erect, whitish ovate-lanceolate or oblongsheathing base, margins plane to slightly incurved, becoming denticulate in subula particularlynear the apex; costa excurrent, occupying most of subula, 1/4–1/3 width of leaf at base, subularoughened abaxially; lamina cells of sheathing base linear to oblong-linear, linear-flexuose orrectangular, becoming rectangular distally and quadrate to short-rectangular in subula.Specialized asexual reproduction unknown. Sexual condition autoicous, paroicous or synoicous;perigonia axillary, or on short branches proximal to perichaetium; perichaetial leaves notdifferentiated. Seta yellow-brown to reddish, elongate, erect. Capsule erect and symmetric orinclined and asymmetric, exserted, brown, cylindric to ovoid-cylindric, ± wrinkled when dryand empty; annulus of 2–3 rows of large, pale cells, deciduous; operculum conic, straight;peristome single, teeth16, variously split to near the base into 2(–3) minutely papillose filaments,teeth sometimes arranged in 8 groups of 2 teeth. Calyptra cucullate. Spores globose to ovoid,finely papillose.

Species 14 (3 in the flora): worldwide.Distichium capillaceum var. curvatum Flowers was described as a probable hybrid between

D. capillaceum and D. inclinatum, characterized by capsule cylindric and strongly curved, andspores 20–23 µm.

1. Capsule erect, cylindric, straight to slightly arcuate, spores 15–25 µm . . . . . . . . . . 1. Distichium capillaceum1. Capsule inclined, ovoid to oblong-ovoid, spores more than 25 µm.

2. Peristome with a yellowish to hyaline basal membrane uniting teeth into 8 separatedgroups each of 2 teeth . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2. Distichium hagenii

2. Peristome of 16, evenly spaced, irregularly divided or perforate teeth . . . . . . . . 3. Distichium inclinatum

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DITRICHACEAE 449·1. Distichium capillaceum (Hedwig) Bruch & Schimper,

Bryol. Europ. 2: 156. 1846

Cynontodium capillaceum Hedwig,Sp. Musc. Frond., 57. 1801

Stems to ca. 6 cm, occasionallylonger. Sexual condition paro-icous. Seta to 2 cm, straight tosomewhat flexuose, smooth, redor reddish brown, occasionallyyellowish brown. Capsule brown,1–2 mm, erect, cylindric to ovoid-

cylindric, straight to weakly arcuate, becoming ± wrinkledwhen dry; operculum to 0.5 mm; peristome teeth evenlyspaced, lanceolate, divided nearly to the base into 2(–3)filaments, smooth to papillose or sometimes ± striolate.Spores densely and finely papillose, 15-25 µm.

Capsules mature summer–fall. Soil, rock, crevices,ledges, banks, occasionally bark; Greenland; Alta, B.C.,Man., N.B., Nfld. and Labr., N.W.T., N.S., Nunavut,Ont., Que., Sask., Yukon; Alaska, Ariz., Calif., Colo.,Idaho, Ind., Iowa, Maine, Mich., Mont., Nev., N.H.,N.Mex., N.Y., N.Dak., Oreg., S.Dak., Utah, Vt., Wash.,Wis., Wyo.; Mexico; Central America; South America;Eurasia; n, c, e, se Asia; Africa; Pacific Islands; Australia;Arctic; Antarctic.

Plants of Distichium capillaceum form dense, rathersilky tufts and the slender, spreading, distichous leaveswith shiny, whitish, oblong, sheathing bases arecharacteristic. This is a taller species than D. inclinatum,with plants less crowded, capsules erect-symmetrical andcylindric, and spores smaller. In more northerly or alpineregions with more severe climatic conditions, the plantsare often shorter, more compact, and have shorter leaves.

2. Distichium hagenii H. Philibert, Rev. Bryol. 23: 36,plate 1, figs. 2, 3. 1896

Distichium inclinatum subsp.hagenii (H. Philibert) J. J. Amann;D. inclinatum var. hagenii(H. Philibert) Mönkemeyer

Stems to ca. 2 cm, occasionallylonger. Sexual condition paro-icous or synoicous. Seta to 2 cm,straight to somewhat flexuose,smooth, red or reddish brown,

occasionally yellowish brown. Capsule brown, 1–1.5mm, inclined, ovoid to oblong-ovoid, becoming± wrinkled when dry; operculum to 0.3 mm; peristometeeth 16, united below by a pale yellow or hyalinemembrane, the teeth in 8 groups of 2, irregularly splitand perforated, smooth or very finely papillose. Sporesfinely papillose to roughened, 30–45 µm.

Capsules mature late summer–fall. Usually calcareoussoil, often in frost cushions; low to high elevations;Greenland; N.W.T., Nunavut; Alaska; n and ArcticEurope; e Asia (China, Mongolia); Arctic Asia (Siberia).

Distichium hagenii is a primarily high Arctic or highelevation species, morphologically close to D. inclinatumand sometimes considered as synonymous with thatspecies. The primary difference is in the peristome. The16 peristome teeth of D. hagenii are grouped in eightpairs united by a pale yellowish basal membrane, eachtooth irregularly split and perforate. A report of thespecies from Newfoundland is referable to D. inclinatum(redetermined by G. R. Brassard according to H. A. Crumand L. E. Anderson 1981). In the southern part of theEuropean range, it grows on sandy or loam soil close tothe sea.

3. Distichium inclinatum (Hedwig) Bruch & Schimper,Bryol. Europ. 2: 157. 1846

Cynontodium inclinatum Hedwig,Sp. Musc. Frond., 58. 1801

Stems to ca. 3 cm, mostly shorter.Sexual condition autoicous. Setato 2 cm, straight to somewhatflexuose, smooth, red or reddishbrown, occasionally yellowishbrown. Capsule brown, 1–1.5mm, inclined, ovoid, becoming

± wrinkled when dry; operculum to 0.3 mm; peristomeevenly spaced, lanceolate, divided nearly to the base into2(–3) filaments, smooth to papillose or sometimes± striolate. Spores densely and finely papillose,occasionally roughened, 30–45(–48) µm.

Capsules mature summer–fall. Calciphilic, sandy soils,rocks, ledges; low to high elevations; Greenland; Alta.,B.C., Man., N.B., Nfld. and Labr., N.W.T., Nunavut,Ont., Que., Yukon; Alaska, Calif., Colo., Mich., Minn.,Mont., Nev., N.Y., N.Dak., Utah, Wis., Wyo.; Mexico;Europe; Eurasia; e, c, n Asia; Arctic.

Distichium inclinatum is similar to D. capillaceum andD. hagenii, differing from the former in the inclined, ovoidcapsule, shorter stems, more closely set leaves, and largerspores. It differs from the latter primarily by features ofthe peristome: the peristome teeth of D. hagenii have abasal membrane and the teeth are arranged in eightirregular but separated groups of two teeth each, ratherthan being evenly spaced as in D. inclinatum andD. capillaceum.

Distichium

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450 DITRICHACEAE

3. DITRICHUM Hampe, Flora 50: 181. 1867, name conserved · [Greek di-, two, andtrichos, hair, alluding to peristome split longitudinally into two segments]

Rodney D. Seppelt

Robert R. Ireland Jr.

Harold Robinson

Plants in loose to dense tufts, green to yellowish green distally, yellow-brown to brownproximally. Stems short or reaching 2 cm or more, simple or sometimes with a few branches;rhizoids at base, smoth. Leaves rigid to flexuose or sometimes somewhat falcate when dry,erect-spreading when wet, lanceolate to subulate from a more or less sheathing base; marginsentire throughout or denticulate near the apex; costa percurrent or excurrent, occupying mostof subula, 1/6–1/3 width of leaf base, 1 row of guide cells, 2 stereid bands, adaxial stereid bandsometimes weak, rarely absent; medial lamina cells quadrate to short-rectangular, becominglonger and thinner-walled proximally toward margins, smooth or rarely papillose at both ends.Specialized asexual reproduction occasionally by rhizoidal tubers. Sexual condition monoicousor dioicous; perichaetial leaves usually with a longer and more or less sheathing base and shortersubulate than stem leaves. Seta pale yellow to dark reddish brown, elongate, erect or flexuose.Capsule mostly erect and symmetric, sometimes ± inclined and arcuate, exserted, ovoid tocylindric, smooth; annulus present, deciduous; operculum conic to short-rostrate; peristomesingle, teeth16, split into 2 filiform segments or sometimes irregularly perforate or split, withor without a short basal membrane, papillose to spiculose. Calyptra cucullate. Spores globose,very finely papillose, verrucose, or with somewhat vermicular ornamentation.

Species ca. 90 (11 in the flora): worldwide, including maritime Antarctic region.Ditrichum occurs from near sea level up to montane regions, on a wide range of soils, but is

found occasionally on rock; some species are calciphilic.

1. Plants densely tufted, stems ± tomentose proximally.2. Stems 1–4 cm; leaves to 3 mm, from an ovate-sheathing base sharply contracted to the

subula; costa abaxially strongly convex; lamina cells near costa with weakly noduloselongitudinal walls; plants commonly fruiting . . . . . . . . . . . . . . . . . . . . . . . . . . . 2. Ditrichum flexicaule

2. Stems to 7 cm or more; leaves from an elongate-ovate base tapering gradually to thelong slender subula; costa abaxially weakly convex; basal laminal cells with weakly tostrongly nodulose longitudinal walls; rarely found fruiting . . . . . . . . . . . . . . . . . . . . 3. Ditrichum gracile

1. Plants loosely to densely tufted or gregarious; stems, if tomentose, only so at extreme base.3. In cross section, distal leaf lamina partially 1-stratose with 2-stratose margins.

4. Leaves erect-appressed to erect-patent when moist.5. Leaves oblong-lanceolate, widest proximally to middle, tapering to a blunt apex;

lamina cells thin-walled, rectangular throughout, slightly shorter and narrowertowards apex; seta to 2.5 cm, yellowish to orange-brown, erect; peristome teeth200–220 µm, perforate, divided into 2 adhering filaments, finely papillose

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5. Ditrichum lineare5. Leaves lanceolate to linear-lanceolate, gradually acuminate; lamina cells

± incrassate, subquadrate to short-rectangular distally, elongate-rectangularproximally; seta to 1.5 cm, reddish with age; peristome teeth 200–250 µm, thefilaments finely and obliquely ridged and lightly papillose . . . . . . . . . . . . 8. Ditrichum pusillum

· Ditrichum

DITRICHACEAE 451·4. Leaves erect-spreading when moist.

6. Stems fastigiately branched from base, dichotomous distally; leaves linear-lanceolate, margins subserrulate distally, apex coarsely toothed; seta to 2.5 cm,pale yellow; capsule straight and erect or slightly curved, orange- to dark red-brown at maturity, elliptical, narrowed at mouth, 2–3 mm, flattened when dry;peristome teeth 600–800 µm, spiculose-papillose; autoicous . . . . . . . . 6. Ditrichum montanum

6. Stem branching distally from base; leaves lanceolate to linear-lanceolate,margins entire to serrulate distally, apex weakly toothed; seta shorter, 0.8–2cm, red to orange-brown; capsule symmetric to slightly curved, 1–3 mm, notflattened when dry; peristome teeth 200–500 µm, papillose to spiculose; dioicous.7. Stems to 2 cm, often branched; leaves 1.5–4.5 mm, apex entire or serrulate,

margins broadly recurved from base to leaf middle; leaf cross section 2-stratose on margins and sometimes near costa; seta 1.5–2 cm, red; capsuleusually symmetric, straight and erect, rarely curved, 1.5–3 mm long, darkbrown to reddish; peristome teeth 200–500 µm, twisted when dry . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1. Ditrichum ambiguum

7. Stems to 0.5 cm, seldom branched; leaves 1–3 mm, apex serrulate, marginsplane or narrowly recurved from above leaf base to leaf middle; leaf crosssection 2-stratose only at or near margins; seta 0.8–1.2 cm, orange-yellow,brownish or reddish; capsule usually asymmetric, erect, curved, 1–2 mm,yellow or light brown; peristome teeth 200 µm, nearly straight . . 11. Ditrichum tortuloides

[3. Shifted to left margin.—Ed.]3. In cross section, distal leaf lamina 2-stratose from costa to margins.

8. Stem leaves 1.5–3 mm, from an ovate to oblong base gradually tapered to a channelledsubula, erect-patent to subsecund; dioicous . . . . . . . . . . . . . . . . . . . . . . . . . . 4. Ditrichum heteromallum

8. Stem leaves longer, 3–7 mm, long-subulate from an ovate to short-rectangular base,spreading, flexuose to subsecund; autoicous.9. Leaves to 5 mm; seta to 2.5 cm, orange-yellow, becoming reddened at maturity;

capsule ovoid-cylindric, ± asymmetric and slightly curved, pale brown, suberect,flattened when dry; peristome teeth to 1500 µm, densely spiculose-papillose; sporesyellow-brown, 11–19 µm, vermicular papillose-verrucose . . . . . . . . . 9. Ditrichum rhynchostegium

9. Leaves 3–7 mm; seta 1–3 cm, yellow or becoming reddish brown at the base whenmature; capsules subcylindric to cylindric, not flattened when dry; peristome teethto 800 µm, finely papillose to spiculose-papillose; spores brown, 15–30 µm, coarselyroughened-papillose.10. Leaves long-subulate from a short-ovoid sheathing base; seta to 2.5 cm, yellow,

becoming reddened at the base with maturity; capsule suberect, subcylindric,1–2.5 mm; peristome teeth pale brown to orange-brown, 300–800 µm, spiculose-papillose; spores 15–30 µm . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7. Ditrichum pallidum

10. Leaves narrow filiform-subulate from an ovate-lanceolate sheathing base; seta1–3 cm, yellow; capsule cylindric, 1.5–3 mm; peristome teeth pale yellow-brown,to 300 µm, irregularly perforate, finely papillose; spores 20–30 µm . . . 10. Ditrichum schimperi

1. Ditrichum ambiguum Best, Bull. Torrey Bot. Club 20:117. 1893

Plants in loose to dense tufts, greento yellowish green, becomingyellowish brown with age, dull.Stems 0.7–2 cm, with a fewreddish rhizoids at the base.Leaves erect-spreading, somewhatcrisped when dry, 1.5–4.5 mm,lanceolate to linear-lanceolate,channelled, lamina with a few

scattered 2-stratose cells midway between margins andcosta in median to distal part of leaf; margins broadly

recurved from the base to near mid lamina, weakly tostrongly serrulate from mid lamina to apex, entire orserrulate at the somewhat blunt apex, 2-stratose distallyand sometimes extending inward for several cells; costadistinct, percurrent, occupying 1/6–1/3 the width of theleaf base; lamina cells thick-walled, distal cells quadrate,irregularly sub-quadrate to short-rectangular, 8–24 × 4–8 µm, becoming broader and longer near the base.Specialized asexual reproduction unknown. Sexualcondition dioicous. Seta red, 1–2 cm, erect. Capsuleerect, usually straight and symmetric or sometimes slightlycurved, dark brown or reddish, cylindric, 1.5–3(–3.2)mm, occasionally slightly enlarged at base; operculum

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Ditrichum

452 DITRICHACEAE

rostrate, 0.4–0.8 mm; peristome red, 200–500(–800) µm,twisted when dry, teeth divided to near base into twoequal filaments, strongly papillose to spiculose. Sporesround, 6–13 µm, appearing smooth to minutely papillose.

Capsules mature spring and summer (Apr–Jul). Moist,sandy or sometimes clay banks, soil on upturned stumps,crevices of sandstone cliffs, often in clearings along roads;low to moderate elevations (100–500 m); B.C. (includingQueen Charlotte Island); Alaska, Calif., Oreg., Wash.;Central America (Guatemala, Panama).

Ditrichum ambiguum, a western species, is very closeto an eastern species, D. tortuloides, but differs in thefollowing morphological characters: stems oftenbranched and taller, 7–20 mm compared to the shorter,2–5 mm, usually simple stems of D. tortuloides; leafmargins broadly recurved, entire or serrulate at asomewhat blunt apex, compared to the narrowlyrecurved, serrate to strongly serrate margins from mid-leaf to an acute apex in D. tortuloides; leaf laminae with2-stratose margins and occasional 2-stratose regionsbetween the margins and the costa in the middle to distalhalf of the leaf, compared to the 2-stratose regions onlyon the margins in D. tortuloides; capsules dark brown toreddish, 1.5–3.2 × 0.2–0.5 mm, straight and symmetricto rarely slightly arcuate with an occasionally slightlyswollen base, compared to the yellow or light brown, 1–2.5 × 0.2–0.3 mm, curved and asymmetric capsules often

with a swollen base in D. tortuloides. The geographicranges of the two taxa are quite disparate. The specieshas been reported outside North America by B. H. Allen(1994), from Guatemala and Panama.

2. Ditrichum flexicaule (Schwägrichen) Hampe, Flora50: 182. 1867

Cynodontium flexicauleSchwägrichen, Sp. Musc. Frond.Suppl. 1(1): 113, plate 29. 1811

Plants usually in dense tufts, greento brownish green, dull. Stems1–4 cm, usually tomentose prox-imally, sometimes only slightly so,± matted together. Leaves stiff toflexuose, rarely ± falcate, to ca. 3

mm, from an ovate to elongate-ovate, sheathing basecontracted rather suddenly to the subula, lamina 1-stratose; margins entire or very weakly denticulate at theapex, often 2-stratose distally on the margins; costaoccupying 1/4–1/3 width of the leaf base, ± convexabaxially, in section with weakly defined adaxial andabaxial stereid bands; cells of the subula short-rectangularto elongate-rhomboid, becoming more elongate in thebase, cells adjacent to the costa with only weakly noduloselongitudinal walls, narrower towards the margins.

DITRICHUM

· Ditrichum

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DITRICHACEAE 453·Specialized asexual reproduction unknown. Sexualcondition dioicous; male plants shorter than femaleplants. Seta dark red-brown, to 2 cm, ± flexuose. Capsule± erect, dark brown, cylindric, to 1.5 mm; operculumhigh- conic to conic-rostrate, 0.7–0.9 mm; peristome teeth2-fid nearly to the short basal membrane, denselyspiculose-papillose, light brown proximally, pale distally,300–450 µm. Spores 9–12 µm, finely papillose.

Capsules seldom produced, mature summer (Jun–Jul).Calciphilic, rock or soil over rock, especially bluffs, cliffshelves or crevices of cliffs, usually in dry and exposedplaces; low to high elevations; Greenland; Alta., B.C.,Man., N.B., Nfld. and Labr., N.W.T., N.S., Nunavut,Ont., Que, Sask., Yukon; Alaska, Colo., Idaho, Mich.,Minn., Mont., Wash., Wyo.; Central America(Guatemala); Europe; Asia; Pacific Islands (New Guinea,New Zealand).

Ditrichum flexicaule in the broad sense (including D.gracile) is exceedingly variable in morphology, not onlyin North America (A. J. Grout 1928–1940, vol. 1, part1; H. A. Crum and L. E. Anderson 1981) but throughoutthe world (R. D. Seppelt 1982; A. A. Frisvoll 1985).While many workers have treated the variation and thedescribed variant taxa as one highly polymorphic species(Crum and Anderson; M. F. V. Corley et al. 1981), others(Frisvoll; E. Nyholm 1986+, fasc. 1; I. Novotny 1996)have recognized two principal entities, D. flexicaule andD. crispatissimum (= D. crinale (Taylor) Kuntze). Wehave followed this latter interpretation. A comprehensivemolecular analysis of the group would be highly desirable.Crum and Anderson related all variation in habit andmicroscopic details to environmental conditions,particularly shade and moisture. Frisvoll differentiatedtwo taxa largely on the basis of gametophytic features.Notwithstanding the considerable variability exhibitedby these taxa, we also consider them distinct. While oftenfound infertile, D. flexicaule is more commonly foundwith sporophytes than is D. gracile. Both are calciphiles.

3. Ditrichum gracile (Mitten) Kuntze, Revis. Gen. Pl. 2:835. 1891

Leptotrichum gracile Mitten,Hooker’s J. Bot. Kew Gard. Misc. 3:353. 1851; L. crispatissimumMüller Hal.; Ditrichumcrispatissimum (Müller Hal.) Paris;D. giganteum R. S. Williams

Plants in tufts, yellowish brown todark green, often shiny. Stemsvery variable in length, to 7 cm or

more, simple or with relatively few branches; looselycompacted and then sparsely tomentose, or closelycompact and rather densely tomentose. Leaves often± falcate, slightly or not flexuose, subula of leaves oftenspirally twisted together, 4–7 mm, tapering ± gradually

from an elongate ovate sheathing base to a long subula,lamina 1-stratose proximally, often 2-stratose distally inthe subula; margins spinulose-denticulate in distal partof the subula or sometimes ± entire, often 2-stratosedistally; costa occupying 1/4–1/3 width of leaf base, weaklyabaxially convex, with poorly developed stereid bandsabaxially and adaxially; cells of the subula and distalpart of leaf base short, isodiametric to rhomboid to shortrectangular, those of the leaf base becoming elongate,rectangular, with ± nodulose longitudinal walls,particularly near the costa, cells of the basal marginsnarrower. Specialized asexual reproduction unknown.Sexual condition dioicous; sporophytes rare; male plantsslightly smaller than rarer female plants. Seta darkreddish brown, to 2.5 cm, ± flexuose. Capsule erect andsymmetric to slightly inclined, dark brown, ± cylindric,1.5–2 mm; operculum high-conic to conic-rostrate, toabout 1 mm; peristome teeth about 400 µm, pale, 2-fid,divided to near base, densely papillose, fragile. Spores12–15 µm, finely papillose.

Capsules rarely produced, mature summer (Jul). Soil,rocks; moderate to high elevations (to 4000 m);Greenland; B.C., Nfld. and Labr., N.W.T., Nunavut, Ont.,Que.; Alaska, Colo., Minn., Mont., Wyo.; Mexico;Central America (Guatemala, El Salvador); SouthAmerica (Colombia); Europe; Asia (Japan, Taiwan);Pacific Islands (New Guinea, New Zealand).

B. H. Allen (1994) included Ditrichum crispatissimumand D. giganteum as synonyms of D. gracile, aninterpretation we have followed here. As with D.flexicaule, a detailed molecular analysis of this and relatedtaxa may help considerably in ascertaining taxonomicaffinities.

4. Ditrichum heteromallum (Hedwig) E. Britton in N. L.Britton et al., N. Amer. Fl. 15: 64. 1913

Weissia heteromalla Hedwig, Sp.Musc. Frond., 71. 1801;Didymodon homomallus Hedwig;Ditrichum homomallum (Hedwig)Hampe; D. zonatum (Bridel)Kindberg; D. zonatum var.scabrifolium Dixon

Plants in loose to dense tufts,yellowish green. Stems to 1 cm,

simple, seldom branched. Leaves 1.5–3 mm, erect-spreading, sometimes slightly secund, from an ovate tooblong base tapering gradually to a long channelledsubula, lamina 2-stratose distally; margins plane, 1-stratose proximally, 2-stratose in the middle to distalparts; costa broad, occupying most of the subula, insection with a distinct abaxial and poorly developedadaxial stereid band; cells of subula and distal laminaelongate-rectangular, longer in the leaf base, smooth orsometimes papillose at both ends, especially near leaf

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Ditrichum

454 DITRICHACEAE

apices. Specialized asexual reproduction by rarelyproduced rhizoidal tubers. Sexual condition dioicous.Seta reddish brown, 1–2.5 mm. Capsule erect, reddishbrown, oblong to cylindric, symmetric, 0.5–1.5 mm;peristome teeth pale orange, about 300 µm, lightlypapillose; operculum conic-rostrate, blunt, 0.4–0.5 mm.Spores 10–15 µm, finely papillose.

Capsules mature summer (Jun–Aug). Soil; low to highelevations (50–1500 m or higher); B.C.; Alaska, Oreg.,Wash.; South America (Colombia); Europe; Asia (China,Japan, Taiwan); Atlantic Islands (Iceland).

Rhizoidal tubers were first reported for Ditrichumheteromallum by S. Risse (1985) from European materialand have also been noted in Japanese material by H.Deguchi and T. Matsui (1986). They have the appearanceof short filaments with swollen, contorted rhizoid cells.Ditrichum zonatum (Bridel) Kindberg, including the var.scabrifolium Dixon, appears to be only a small form ofD. heteromallum with shorter, appressed leaves that areoften more 2-stratose, especially near the base, and leafcells that are sometimes papillose at the ends. We havenot seen specimens that support the Wisconsin report byF. Bowers and S. Freckman (1979) and believe the recordto be dubious.

5. Ditrichum lineare (Swartz) Lindberg, Acta Soc. Sci.Fenn. 10: 108. 1871

Didymodon linearis Swartz, Adnot.Bot., 100. 1829; Ditrichumvaginans (Sullivant) Hampe;Trichostomum vaginans Sullivant

Plants in loose to dense tufts,yellowish green. Stems to 1(–1.5)cm, simple or with few branches.Leaves to 2 mm, erect and ± ap-pressed to the stem, oblong-

lanceolate, widest at or slightly just proximal to themiddle, tapering gradually to a rather blunt apex, lamina1-stratose except on margins; margins subentire, planeto narrowly recurved, ± erect near the apex, irregularly2-stratose in the distal half of the leaf; costa percurrent,broad, occupying about 1/3 width of the leaf base, insection with a weakly developed stereid band on abaxialside of guide cells; cells of proximal part of laminarectangular, thin to moderately thick-walled, becomingslightly shorter and narrower towards the leaf apex.Specialized asexual reproduction by rhizoidal tubers.Sexual condition dioicous; perichaetial leaves with asheathing base, abruptly narrowed to a short subulaabout as long as the base or shorter. Seta yellowish,brown to orange-brown with age, to 2.5 cm or sometimeslonger, erect. Capsule erect and symmetric or slightlycurved, brown to reddish brown, narrowly ellipsoid tocylindric, 1–2 mm, smooth or indistinctly furrowed whendry; operculum obliquely conic-rostrate, blunt, 0.3–0.7

mm; peristome divided by perforations into 2 ± adheringdivisions, 200–220 µm, finely papillose. Spores 13–16µm, appearing smooth or very finely verrucose, brown.

Capsules mature spring (Apr–May). A pioneer species,bare clay, sandy or gravely soil banks, wooded clearings,trails, roads and other often disturbed habitats; lowelevations; N.B., Nfld. and Labr., N.S., Ont., P.E.I., Que.;Ala., Ark., Del., D.C., Conn., Fla., Ga., Ill., Ind., Iowa,Ky., Maine, Md., Mass., Mich., Mo., N.H., N.J., N.Y.,N.C., Ohio, Pa., R.I., Tenn., Vt., Va., Wis.; Europe;e Asia (Japan).

Rhizoidal tubers, consisting of swollen rhizoidal cellsand arising laterally from axial rhizoids, are known forDitrichum lineare only from Asia (T. Matsui et al. 1985;Matsui and Z. Iwatsuki 1990). This species is very similarin appearance to D. pusillum but is distinguished by therectangular cells of the sheathing leaf base. The leafmargins of North American specimens of D. lineare areentire and plane or rarely only weakly recurved,irregularly 2-stratose but not noticeably thickened, andthe lamina cells are elongate rectangular to linear. Theleaf margins in D. pusillum are irregularly thickened,serrulate, more strongly recurved, and the lamina cellsgenerally subquadrate to short-rectangular. Ditrichumlineare also has a subula shorter than the sheathing base,which is unusual in the genus. This macroscopic featureis sometimes used to distinguish it from the closely relatedD. pusillum, which has a subula longer than the sheathingbase, typical of many species in the genus (R. R. Ireland1982).

6. Ditrichum montanum Leiberg, Bull. Torrey Bot. Club20: 112, plate 143. 1893

Plants usually in tufts, green.Stems erect, to 2 cm, fastigiatelybranched from near base,dichotomous distally. Leavesspreading when moist, erect andsomewhat contorted when dry,linear-lanceolate, lamina 1-stratose except on margins;margins plane proximally, erect to

slightly incurved distally, 2-stratose and subserrulatedistally, the apex blunt and coarsely toothed; costa broad,strong, ceasing shortly just proximal to the apex, insection with strong abaxial and weak adaxial stereidbands; lamina cells thick-walled, rectangular proximally,becoming ± quadrate distally. Specialized asexualreproduction unknown. Sexual condition autoicous;perigonia terminal on short basal or axillary branches;exterior perichaetial leaves similar to stem leaves, theinner broadly sheathing. Seta pale yellow, to 2.5 cm,erect. Capsule straight and erect or slightly curved,orange-brown, dark reddish brown at the mouth,elliptical, narrowed at the mouth, 2–3 mm, flattened and

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· Ditrichum

DITRICHACEAE 455·weakly sulcate when dry; operculum conic-rostrate, to 1mm; peristome 600–800 µm, often broken, the teeth splitto the short basal membrane, spiculose-papillose. Spores8–10 µm, appearing smooth.

Capsules mature summer (Jul–Aug). Soil, montanehabitats; moderate to high elevations (800–1600 m);Alta., B.C.; Idaho, Oreg., Wash.

Ditrichum montanum is apparently confined to uplandhabitats on disturbed soil. It is distinguished from D.heteromallum by the short, more or less quadrate cells inthe distal part of the leaf and by the pale, yellowish seta.Elevation data are from E. Lawton (1971).

7. Ditrichum pallidum (Hedwig) Hampe, Flora 50: 182.1867

Trichostomum pallidum Hedwig, Sp.Musc. Frond., 108. 1801;Ditrichum currituckii Grout

Plants rather small, in silky greento yellowish green, loose tocompact tufts. Stems short, to0.5(–1) cm, usually simple. Leaveserect-spreading to subsecund,flexuose-contorted when dry, to 7

mm; from a short ovate-lanceolate and ± sheathing basegradually or rather shortly narrowed to an elongatesubula, lamina 2-stratose distally; margins erect,becoming serrulate towards the apex, 1-stratoseproximally, 2-stratose in the subula; costa rather thin andnarrow at the base, broader distally and occupying mostof the base of the subula, excurrent, in section with abroad band of guide cells and shallow adaxial and abaxialstereid bands; cells of the leaf base rectangular to oblong-hexagonal, narrowed towards the margin and forming a± distinct hyaline zone, elongate-rectangular in distal leafbase and subula. Specialized asexual reproductionunknown. Sexual condition autoicous; perigonia axillary;perichaetial leaves shorter than stem leaves, the base notsheathing. Seta yellow or sometimes reddish brown nearbase, elongate, to 4 cm or occasionally longer, flexuose.Capsule suberect to somewhat inclined, yellow tobrownish yellow, reddish brown with age, subcylindric,with a broadened base tapering gradually to a narrowedmouth, 1–2.5 mm, slightly asymmetric, weakly furrowedwhen dry and empty; operculum conic-rostrate, to about0.8 mm; peristome 300–800 µm, pale brown to yellowishorange, 2-fid to a very short basal membrane, denselyspiculose throughout. Calyptra long-cucullate. Sporesrounded to obscurely tetrahedral, 15–30 µm, coarselyand sparsely papillose, brown.

Capsules mature winter–summer (Feb–Jul). Sandy orclay soil, rather dry, open or partly shaded habitats; lowelevations; N.B., N.S., Ont., Que.; Ala., Ark., Conn.,D.C., Fla., Ga., Ill., Ind., Iowa, Kans., Ky., La., Maine,Md., Mass., Mich., Miss., Mo., N.J., N.Y., N.C., Ohio,

Okla., Pa., S.C., Tenn., Tex., Va., Vt., W.Va., Wisc.;Europe; e Asia (Japan); c Africa.

When Ditrichum pallidum is fruiting, the long, yellowsetae are distinctive. The slightly asymmetric capsule andthe long, spiculose peristome teeth are similar to those ofD. difficile (Duby) Fleischer, a widespread, commonspecies occurring in Mexico, Central and South Americaas well as elsewhere throughout the world, and D.rhynchostegium. However, the spores of all three speciesare easily distinguished. Spores of D. difficile are finelypapillose-verrucose and 12–18(–20) µm; those of D.rhynchostegium are vermicularly papillose-verrucose and11–15(–18) µm; those of D. pallidum are larger, 15–30µm, and the exine ornamentation coarsely and openlypapillose.

Herbarium specimens of Ditrichum pallidum and D.rhynchostegium are sometimes misidentified. If fruiting,the orange to reddish seta of D. rhynchostegium willimmediately distinguish it from D. pallidum with itsyellowish seta. Also, spores of D. rhynchostegium havea distinctly vermicular ornamentation and are smaller.The operculum of D. pallidum is about half the length ofthat of D. rhynchostegium. Vegetatively, plants of D.pallidum have short stems and the leaf base is often ovateto ovate-lanceolate, being gradually narrowed to thesubula. On the other hand, plants of D. rhynchostegiumhave longer stems and the leaf base is oblong-ovate andabruptly narrowed to the subula. L. E. Anderson andV. S. Bryan (1958) discussed the similarity of D.currituckii and D. pallidum, but maintained them asdistinct species. H. A. Crum and Anderson (1980–1983)considered D. currituckii to be a variant form of D.pallidum having shorter capsules and peristomes, slightlyshorter leaves with the costa somewhat broader at thebase. The morphological and cytological differences wereconsidered by Crum and Anderson (1981) to beinsufficient to warrant separation.

8. Ditrichum pusillum (Hedwig) Hampe, Flora 50: 182.1867

Didymodon pusillum Hedwig, Sp.Musc. Frond., 104. 1801;Ditrichum tortile (Schrader)Brockmuller; Trichostomum tortileSchrader; T. tenue Hedwig; Weissiacapillacea Bridel

Plants small, to ca. 1 cm, formingdull green tufts. Stems 0.4–1.2 cm,simple. Leaves to ca. 3.5 mm,

erect-patent, weakly secund, lanceolate to linear-lanceolate, gradually acuminate to a channelled subula,acute, lamina 1-stratose except on margins; marginsbistratose, entire or serrulate near the apex, irregularlythickened and recurved at least in distal half; costa stout,percurrent to excurrent, in section with abaxial stereid

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Ditrichum

456 DITRICHACEAE

band; proximal lamina cells elongate-rectangular, distallamina cells subquadrate to short-rectangular orsomewhat irregular in outline, ± incrassate. Specializedasexual reproduction by rounded to pyriform orirregularly-shaped, yellow to orange rhizoidal tubers, to150 µm. Sexual condition dioicous; perichaetial leavessimilar to stem leaves but with a somewhat longer subulanarrowing more abruptly from the base. Seta becomingreddish with age, to 1.5 cm, erect. Capsule erect, darkbrown to reddish brown, ovoid to cylindrical, symmetric,1–2 mm, smooth to ± furrowed when dry; operculumobliquely conic-rostrate, blunt, 0.3–0.7 mm; peristomesplit nearly to the base into 2 segments, brown, denselyand finely obliquely-ridged and lightly papillose, 200–250 µm. Spores 11–20 µm, appearing ± smooth.

Capsules mature spring–summer (Apr–Jun). Bare,disturbed calcium-free clay, sandy or gravely soil banks,disturbed habitats, especially along roads and trails, andsometimes in cliff crevices; low to moderate elevations;B.C., N.B., Nfld and Labr., N.S., Ont., P.E.I.; Ala., Ark.,Fla., Ga., Ill., Ind., Iowa, Ky., La., Maine, Mass., Mich.,Minn., Mo., Nebr., N.Y., Tenn., Tex., Va., Wis.; Europe;Asia; Africa; Atlantic Islands (Iceland).

When sterile, Ditrichum pusillum is morphologicallyvery similar to D. ambiguum and D. tortuloides. Whensporophytes are present, the dense, fine, obliquely striateperistome teeth with weak papillae immediatelydistinguish D. pusillum from those two species, whichhave spiculose peristome teeth. The spores of D. pusillum(10–19 µm) are also larger compared to those of D.ambiguum (6–11 µm) and D. tortuloides (9–13 µm). Adiscussion of the relationships of D. pusillum with bothD. ambiguum and D. tortuloides was given by R. R.Ireland and H. Robinson (2001).

9. Ditrichum rhynchostegium Kindberg, Rev. Bryol. 37:14. 1910

Ditrichum henryi H. A. Crum &L. E. Anderson

Plants in low, silky green toyellowish green tufts or looselygregarious. Stems to 1 cm, simple.Leaves to 5 mm, erect to some-what flexuose and spreading,rather crisped or contorted whendry, linear-subulate from a rather

suddenly widened, subsheathing base, subula channelleddistally, lamina 2-stratose distally; margins erect, slightlydenticulate close to the apex, 2-stratose in the subula;costa broad and flat, occupying ca. 1/4 of the leaf base,percurrent, occupying most of the subula, in section witha prominent abaxial and weak adaxial stereid band; cellsof the leaf base rather laxly oblong-hexagonal, wider near

the costa, narrower and shorter near the margins,becoming shorter and subquadrate to short-rectangularand thicker-walled in distal sheath, short-rectangular toquadrate in the subula. Specialized asexual reproductionunknown. Sexual condition autoicous; perigonia axillary;perichaetial leaves with a ± sheathing base. Seta orange-yellow becoming reddish at maturity, elongate, 2–5 cm,slender, flexuose. Capsule suberect to inclined, palebrown, ovoid cylindric when moist, slightly asymmetric,2.5–3.5 mm, flattening when dry and empty, narrowedat the mouth; operculum tall-conic, tapering to a bluntapex, to 1.5 mm; peristome teeth pale brown, to 1500µm, split almost to the base into two long, filiform,densely spiculose filaments. Spores rounded to rounded-tetrahedral, 11–15(–19) µm, vermicular papillose-verrucose, yellowish brown.

Capsules mature summer (Jun–Aug). Sandy or claysoil, clearings in woods, banks of trails, sometimes overrocks and along streams; low elevations; N.S., P.E.I.; Ark.,Ga., Ky., La,, Md., N.C., Ohio, Pa., S.C., Tenn., Va.,W.Va.; Asia (Japan, Korea, Taiwan).

The type collection of Ditrichum rhynchostegiumappears to have been lost, but comparison of materialcollected from the type locality with the originaldescription left little doubt that it represented a distinctspecies, and that D. henryi is synonymous (H. Robinson1966). Ditrichum rhynchostegium has been confusedwith D. pallidum but is readily distinguished from thatspecies superficially and microscopically (see discussionunder 7. D. pallidum). The report of D. rhynchostegiumfrom the District or Columbia by R. R. Ireland (1982) iserroneous.

10. Ditrichum schimperi (Lesquereux) Kuntze, Revis.Gen. Pl. 2: 835. 1891

Leptotrichum schimperi Lesquereux,Mem. Calif. Acad. Sci. 1: 9. 1868

Plants in tufts or gregariouspatches, yellowish green. Stems to0.6 cm, rarely to 1 cm, simple.Leaves crowded, erect-spreadingto slightly secund, ± contorted, 3–7 mm, narrow filiform-subulatefrom an ovate to lanceolate base,

lamina 2-stratose distally; margins plane to incurved, 1-stratose proximally, 2-stratose distally in subula, entireor slightly serrulate near the apex; costa broad, percurrentto excurrent, occupying the width of the subula near theapex, ca. 1/4 width of leaf at base, in cross section with anabaxial stereid band and a few adaxial stereids; distallamina cells short-rectangular, becoming elongate andrectangular proximally, narrower and longer towards themargins; perichaetial leaves with a sheathing base.Specialized asexual reproduction unknown. Sexual

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· Ditrichum

DITRICHACEAE 457·

condition autoicous; perigonia in small buds justproximal to the perichaetium. Seta yellow, 1–3 cm, erectto flexuose. Capsule erect to inclined, yellowish toyellowish brown, somewhat reddish brown with age,cylindric, 1.5–3 mm, weakly sulcate when dry; operculumshort-rostrate, to about 1 mm; annulus narrow, dehiscent;peristome short, to 300 µm, the teeth irregularly perforateor divided proximally, with a narrow basal membrane,finely papillose distally, nodose proximally. Calyptralarge, cucullate and twisted. Spores 20–30 µm,roughened, brown.

Capsules mature spring (Apr–May). Moist soil; lowelevations; B.C.; Calif., Oreg., Wash.

L. E. Anderson and V. S. Bryan (1958) stated thatDitrichum schimperi is not uncommon from VancouverIsland and south through the Coastal Ranges to YosemiteValley. This is the only Ditrichum species along the westcoast of North America with large and roughenedpapillose spores. Ditrichum pallidum from the easternand southern United States also has large, roughlypapillose spores of similar size, but differs in peristomecharacters. The peristome of D. schimperi is finelypapillose, rather than spinose- or spiculose-papillose, isreduced in size, and is irregularly perforate proximally.

11. Ditrichum tortuloides Grout, Bryologist 30: 4.1927

Plants green to yellowish green,becoming brown with age, dull, inloose to somewhat dense tufts.Stems 2–5 mm, simple or seldombranched, with a few dark redrhizoids near the base. Leaveserect-spreading, slightly crisped tofalcate-secund when dry, 1–3 mm,lanceolate to linear-lanceolate,

channelled, lamina 1-stratose except near margins;margins plane to narrowly recurved from just beyondthe leaf base to mid leaf, serrate to strongly serrate frommid leaf to the acute apex, 2-stratose distally and rarelya cell inward; costa distinct, percurrent, occupying 1/6–1/3 width of the leaf base; lamina cells thick-walled, distalcells 8–24 × 8 µm, becoming slightly broader and longerin the base. Specialized asexual reproduction unknown.Sexual condition dioicous. Seta orange-yellow, brownishor reddish, 0.8–1.2 cm, erect. Capsule erect, yellow orlight brown, curved and asymmetric, 1–2(–2.5) mm, oftenswollen at the base; operculum rostrate, 0.5–0.8 mm;peristome 200 µm, 2-fid, the filaments ± unequal, linear,

DITRICHUM ° SAELANIA

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Ditrichum

458 DITRICHACEAE

somewhat twisted when dry, strongly papillose tospiculose. Spores round, 9–13 µm, appearing smooth tominutely papillose.

Capsules mature spring (Jun). Primarily on serpentinesoils, clearings along roads; moderate elevations (ca. 400m); Md., N.H., Vt.

Ditrichum tortuloides was synonymized by H. A.Crum and L. E. Anderson (1981) with D. ambiguum.However, R. R. Ireland and H. Robinson (2001) discussedreasons for distinguishing the two species. For adiscussion of the similarities and distinguishingcharacteristics, see under 1. D. ambiguum.

4. SAELANIA Lindberg, Utkast Eur. Bladmoss., 35. 1878 · [For Anders Thiodolf Saelan,1834–1921, Finnish botanist]

Rodney D. Seppelt

Plants tufted, glaucous bluish green or sometimes yellowish green. Stems short or reaching 1.5cm, simple or branched; rhizoids at base, papillose or smooth. Leaves somewhat flexuose orcontorted when dry, narrowly lanceolate, gradually acuminate, margins plane or narrowlyrecurved and entire proximally, irregularly and often doubly toothed or serrate distally; costa1, percurrent to short-excurrent, 1/5–1/3 width of leaf base; medial laminal cells smoothsubquadrate to short-rectangular, smoth. Specialized asexual reproduction unknown. Sexualcondition autoicous; perigonia terminal on well-developed branches; perichaetial leaves notdifferentiated. Seta yellow or yellow-brown, elongate, erect. Capsule erect and symmetric,exserted, yellow-brown, cylindric, ± longitudinally plicate when dry and empty; annulus of 2–3 rows of large, pale cells, persistent; operculum rostrate; peristome single, teeth16, split into 2filaments, densely papillose. Calyptra cucullate. Spores globose, finely papillose.

Species 1: North America, Europe, Asia, Africa, Pacific Islands (Hawaii, New Zealand).Saelania is morphologically close to Ceratodon, but differs in having the leaves a glaucous

blue-green; seta yellow to yellow-brown; capsule yellow-brown, erect, and somewhat plicatebut not strongly sulcate when dry; peristome reddish brown, densely papillose, divided to nearthe base into two unbordered filaments; and spores greenish to yellowish brown and larger,15–20(–22) µm. In Ceratodon the leaves are yellowish green to brownish or reddish green;seta reddish to purplish; capsules dark reddish brown to purplish, erect to inclined or horizontal,and when dry usually strongly sulcate; peristome teeth dark red, papillose, divided to near thebase into 2 filiform segments with pale borders and the segments often united at the nodes;and spores yellow to greenish yellow, and smaller (10–15 µm).

1. Saelania glaucescens (Hedwig) Brotherus in J. O.Bomansson and V. F. Brotherus, Herb. Mus. Fenn.,Musci, 53. 1894

Trichostomum glaucescens Hedwig,Sp. Musc. Frond., 112. 1801

Leaves 1–2.5(–3.5) mm, proximalleaves small, the distal andperichaetial leaves graduallyacuminate, ± subulate from alanceolate base; costa with a singlerow of guide cells, and bothadaxial and abaxial stereid bands,

or adaxial stereid band sometimes weak or rarely absent;lamina cells often irregularly 2-stratose towards the apexand occasionally elsewhere. Seta to 15 mm. Capsule

with operculum to 1 mm. Spores 15–20(–22) µm,greenish to yellow-brown.

Capsules mature early summer–late fall. Soil on steepbanks, particularly those protected by overhangs,frequent on roadsides, soil in sheltered rock crevices;moderate to high elevations; Greenland; Alta., B.C.,Man., N.B., Nfld. and Labr. (Nfld.), N.S., Ont., Que.,Yukon; Alaska, Ariz., Colo., Iowa, Mich., Minn., Nebr.,N.J., N.Y.; n Eurasia; e Asia; s Africa; Pacific Islands(Hawaii, New Zealand).

The whitish to bluish coloration of the leaves ischaracteristic. Often thought to have been fungal orcyanobacterial in origin, the granular or thread-likesurface material responsible for the glaucous colorationis a diterpene.

· Ditrichum Saelania·

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DITRICHACEAE 459·5. TRICHODON Schimper, Coroll. Bryol. Eur., 36. 1856 · [Greek trichos, hair, and

odon, tooth, alluding to slender divisions of peristome]

Robert R. Ireland Jr.

Plants scattered or in loose tufts, light- to yellowish green. Stems 0.2–0.4 cm, simple; rhizoidsat base, papillose. Leaves slightly contorted when dry, subulate, tubulose, base broad andsheathing; margins plane or incurved, serrate to enlarged portion of leaf base; costa percurrentto excurrent, filling distal part of subula, strongly prorulose on abaxial surface; medial laminalcells rectangular, sometimes quadrate and irregularly angled on margins, smooth or prorulose.Specialized asexual reproduction sometimes present, as smooth, round or irregularly shapedtubers on rhizoids. Sexual condition dioicous; male and female plants about the same size;perichaetial leaves not differentiated. Seta yellow to red, elongate, erect. Capsule erect toinclined, exserted, yellowish to reddish brown, cylindric, slightly curved or sometimes straight,smooth; annulus of 1–3 rows of large cells, deciduous; operculum conic to short-rostrate;peristome single, teeth 16, divided nearly to base to form two filiform segments, papillose.Calyptra cucullate. Spores globose, minutely papillose.

Species 2 (1 in the flora): North America, Europe, Asia in boreal and arctic areas.

SELECTED REFERENCE Ireland, R. R. 1978. Trichodon in North America. Bryologist 81: 150–154.

1. Trichodon cylindricus (Hedwig) Schimper, Coroll.Bryol. Eur., 36. 1856

Trichostomum cylindricum Hedwig,Sp. Musc. Frond., 107. 1801;Ditrichum cylindricum (Hedwig)Grout

Stems axillary hairs 2 per leaf axil,with 2 short, brown basal cells and3 elongate, hyaline distal cells.Leaves 1–3 mm, acute, basesovate; margins plane, serrate to

serrulate in subulate part; costa percurrent, filling distalparts of the subula, strongly prorulose distally on abaxialsurface; median cells rectangular, 17–39 × 3–5 µm,becoming larger at base. Specialized asexual reproductionsometimes present as yellowish brown, smooth, roundor irregularly shaped tubers borne on rhizoids, 65–100µm in longest dimension; perigonia and perichaetiaterminal. Seta orange to red, erect, straight, 0.3–2.7 cm,twisted when dry. Capsule slightly arcuate or sometimesstraight (0.5–)1–2(–2.5) × 0.2–0.5 mm; operculum 0.3–0.6 mm.

Varieties 2 (2 in the flora): North America, Eurasia.Trichodon cylindricus has a disjunct distribution in

North America, where it is not uncommon in thenorthwestern part of the continent but is known fromonly a few scattered localities in the eastern part. It hasbeen collected from only a single locality each in Michigan(Keewenaw County), New Brunswick, and Ontario, andtwo localities each in Newfoundland and Quebec. The

distinctive gametophytes and sporophytes should aidcollectors in finding additional eastern localities. Thedistinctive characters of this species include the smallplants, 2–4 mm high, with squarrose, subulate, acuteleaves, and the slender, cylindric capsules.

1. Seta 0.5–2.7 cm; capsule mostly inclined, mostlyslightly arcuate (sometimes straight), (0.5–)1–2(–2.5) mm; spores 9–16 µm . . . . . . . . . . . . . . . . . . . . . . . . . . 1a. Trichodon cylindricus var. cylindricus

1. Seta 0.3–1.3 cm; capsule mostly erect, straight toweakly arcuate, (0.5–)1–1.5(–2) mm; spores 19–24 µm . . . . . . . 1b. Trichodon cylindricus var. oblongus

1a. Trichodon cylindricus (Hedwig) Schimper var.cylindricus

Seta 0.5–2.7 cm. Capsule inclined,rarely erect, arcuate (sometimesstraight), (0.5–)1–2(–2.5) mm.Spores 9–16 µm.

Capsule maturity date notdetermined. Sandy or sometimesclay soil, open, disturbed sites,roadside banks, trails, fields; lowto high elevations (30–2000 m);

Alta., B.C., N.B., Nfld. and Labr. (Nfld.), Ont., Que.,Yukon; Alaska, Calif., Idaho, Mich., Mont., Oreg., Wash.;Europe; Asia.

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Trichodon

460 DITRICHACEAE

1b. Trichodon cylindricus var. oblongus (Lindberg)Podpera, Consp. Musc. Eur., 97. 1954

Trichodon oblongus Lindberg,Öfvers. Kongl. Vetensk.-Akad. Forh.21: 226. 1864; Ditrichum boreale(R. S. Williams) Grout

Seta 0.3–1.3 cm. Capsule erect,straight to weakly arcuate,(0.5–)1–1.5(–2) mm. Spores 19–24 µm.

Capsule maturity date notdetermined. Clay soil, exposed and disturbed sites;elevations not recorded; N.W.T., Yukon; Alaska; Europe.

Variety oblongus is an arctic taxon that differs fromvar. cylindricus only in the shorter setae, shorter capsulesthat are more erect and often nearly straight, andsomewhat larger spores.

TRICHODON ° CLEISTOCARPIDIUM

6. CLEISTOCARPIDIUM Ochyra & H. Bednarek-Ochyra, Fragm. Florist. Geobot. 41:

1035. 1996 · [Greek kleistos, unopened, and karpos, fruit, alluding to indehiscentcapsule without operculum]

Kwok Leung Yip

Plants loosely tufted, yellow-green. Stems 0.3–0.8 cm, simple, rhizoids sparse. Leaves looselyerect when dry, subulate from an ovate-lanceolate to narrowly obovate base, margins largelyplane, entire, serrulate along the subula; costa excurrent, subula flexuose; cells 1-stratose, lineardistally, laxly oblong-rhomboidal proximally; perichaetial leaves in transverse section with 6–7

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· Trichodon Cleistocarpidium·

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DITRICHACEAE 461·large guide cells closer to the adaxial side, two stereid bands on either side of guide cells inapical sections, but only one disconnected stereid band at leaf middle and base; laminal cellslaxly oblong-rhomboidal proximally, linear distally, smooth. Sexual condition paroicous (andreportedly autoicous), antheridia naked; perichaetial leaves proximally broadly ovate, abruptlysubulate. Seta short, erect. Capsule cleistocarpous, immersed, ovoid, broader at the base;stomata numerous, scattered in proximal half of the capsule. Calyptra mitraeform to cucullate,regularly 4-lobed at base. Spores globose, densely and finely papillose.

Species ca. 2 (1 in the flora): North America, Europe.The calyptra of Cleistocarpidium is 4-lobed, often with a deep indention on one side. The

cryptoporic stomata are confined to the proximal half of the capsule, but not restricted to theextreme base as is the case with Pleuridium. The pale, ovoid capsule may be slightly asymmetric.This genus includes Sporledera in the sense of European authors but not of Hampe.

1. Cleistocarpidium palustre (Bruch & Schimper)Ochyra & H. Bednarek-Ochyra, Fragm. Florist. Geobot.41: 1035. 1996

Phascum palustre Bruch &Schimper, Mém. Soc. Mus. Hist.Nat. Strasbourg 2(CC): 2. 1835;Astomum palustre (Bruch &Schimper) Hampe; Bruchia palustris(Bruch & Schimper) Müller Hal.;Pleuridium palustre (Bruch &Schimper) Bruch & Schimper;Sporledera palustris (Bruch &Schimper) Schimper

Plants very small. Sexual condition paroicous (andreportedly autoicous). Seta stout, pale, 0.6–1 mm, erect.Capsule immersed, ovoid, broadest at the base, whitish,not glossy, spore sac orange, 1–1.5 × 0.6–0.8 mm,strongly apiculate, stomatose in proximal half. Calyptra

covering the apiculus, mitrate, shallowly 4-lobed tocucullate, deeply split on one side.

Capsules mature early summer (May–Jun). Wet soil,sandy swamps; low to moderate elevations; Del., La.,Md., Mass., N.J., N.Y., Pa., Tenn.; Europe.

The chromosome number is n = 7 (H. A. Crum andL. E. Anderson 1981). Cleistocarpidium palustre (canbe recognized easily by the extremely long subula, whichis flexuose to some degree, the excurrent costa, and thecharacteristic capsule, small rostrum, and mitratecalyptra. In transverse sections of the leaf, the two largestguide cells are at the center of the costa. Although anannulus is absent in the capsule of C. palustre, a non-functional rudimentary ring is present in the rostrumbeyond the spore sac region in C. japonicum (Deguchi,Matsui & Z. Iwatsuki) K. L. Yip, which distinguishesthese two taxa. The latter species was initially recognizedas the former (S. Risse 1991) because of the similargametophytes.

7. ECCREMIDIUM Wilson, London J. Bot. 5: 450. 1846 · [Greek ekkremes, hanging,and -idium, diminutive, alluding to pendulous capsule]

William R. Buck

Plants scattered or in loose to compact turfs, mostly yellowish green, sometimes reddish. Stemserect, to ca. 0.5 mm, sometimes seemingly absent; simple or branched by innovations; rhizoidsat base, smooth. Leaves imbricate to spreading when dry, lanceolate to ovate, acute to subulate;margins plane, entire or serrate; costa subpercurrent to excurrent, sometimes weak or absenttoward insertion and in lowermost leaves, medial laminal cells rhomboidal to short-rectangular,becoming longer toward the insertion, smooth. Specialized asexual reproduction unknown.Sexual condition autoicous or dioicous, cladocarpous; perichaetial leaves sometimesdifferentiated. Seta short, curved at apex, rarely ± erect. Capsule pendulous and laterallyemergent, rarely erect and immersed, reddish at maturity, subglobose; annulus near midurn, of1–2 rows of small cells, persistent; operculum obtuse to apiculate; peristome none. Calyptraconic-mitrate, entire at base or crenate-lobed. Spores globose to reniform, coarsely papilloseto reticulate.

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Cleistocarpidium Eccremidium·

462 DITRICHACEAE

Species 6 (1 in the flora): North America, South America, Asia, Africa, Australia.

SELECTED REFERENCE Crum, H. A. 1981. Eccremidium, a genus of Ditrichaceae new to the Americas. Bryologist 84: 527–532.

1. Eccremidium floridanum H. A. Crum, Bryologist 84:531, figs. 1–10. 1981

Leaves loosely erect, subsecund,ca. 1 (proximal) to 1.6 (distal)mm, longly subulate-acuminatefrom a concave, lanceolate base;margins sharply serrate above theshoulders; costa excurrent, fillingthe subula, often weak or absentnear the insertion; median cellsoblong-rhomboidal, 43–66 × 12–

17 µm, firm-walled, becoming larger at base. Sexualcondition paroicous. Seta stout, arcuate, ca. 1 mm.Capsule laterally emergent, pendulous, ca. 0.7 mm(including operculum); operculum dome-shaped, short-apiculate. Calyptra weakly prorulose near apex. Sporessubreniform, 67–100 µm, granulate-tuberculate on distalface, the ornamentation becoming fused and ± ribbed onproximal face.

Capsules mature Nov–Feb. Sandy or sometimes claysoil in open, disturbed sites, often in areas that are wetpart of the year and quite dry other parts of the year,fields and roadsides, thin soil over rock outcrops, aroundmargins of Taxodium swamps; low elevations (0–70 m);Fla., Ga; South America (Brazil).

Eccremidium floridanum is known in the flora areaonly from the Panhandle of Florida and southern Georgia.It may well be more widespread in the Southeast butappears to be ephemeral, and the plants often die downby early spring, prior to the arrival of most collectors.The species may be the same as the Australian and SouthAfrican E. exiguum (Hooker f. & Wilson) Wilson, withwhich it has much in common. In the field, Americanmaterial looks different from Australian material; in theformer the leaves of fresh plants are decidedly moresubsecund. The distinctive characters of this speciesinclude its minute size, arcuate setae and laterallyemergent capsules dehiscent near mid urn without aperistome.

ECCREMIDIUM ° PLEURIDIUM

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· Eccremidium

DITRICHACEAE 463·8. PLEURIDIUM Rabenhorst, Deutschl. Krypt.-Fl. 2(3): 79. 1848, name conserved

· [Greek, pleura, side or rib, and -idium, diminutive, alluding to sporophytes oftenemerging laterally from perichaetium]

Kwok Leung Yip

Plants gregarious to loosely tufted, yellow-green. Stems 0.3–0.7 cm, simple or branched; rhizoidsat base, smooth. Leaves erect-spreading or appressed when dry, proximal leaves linear to deltoid,distal leaves oblong to lanceolate with subulate to acuminate tips, margins plane andundifferentiated, entire to serrate or abruptly toothed; costa subpercurrent to excurrent,sometimes roughened on the abaxial surface, stereid bands one or two, guide cells centrallylocated, confluent with the cells of the leaf lamina; basal laminal cells quadrate-rectangular,median cells irregular, rhomboidal to trapezoidal, marginal cells slightly longer than adjacentcells; distal cells elongated. Specialized asexual reproduction by innovations and rhizoidal tubers.Sexual condition monoicous; perigonia occur proximal to perichaetium with antheridia generallynaked in leaf axils (paroicous), or in small buds in axils of stem leaves (autoicous); perichaetiasingle, terminal on mature stem, with 3–8 perichaetial leaves similar to the distal cauline leaves.Seta short, erect or curved. Capsule cleistocarpous, erect, immersed, orange to brownish, ovoidto elliptical; stomata 4–10, superficial, restricted to base of capsule. Calyptra mostly persistent,cucullate. Spores spherical, papillose to short-spinose.

Species 21 (4 in the flora): worldwide except Antarctica.Pleuridium is related to Ditrichum, as demonstrated by hybridization (L. E. Anderson 1980)

and by similarities in gametophyte morphology and molecular characters (C. La Farge et al.2000). Pleuridium is also closely related to Cleistocarpidium by the immersed cleistocarpouscapsules but C. palustre has mitrate calyptras and pale whitish capsules, which are asymmetricaland stomatose to the equator. In Pleuridium, sporophytes may emerge laterally from theperichaetium, not because of an actual lateral origin or position, but owing to the curvature ofa short seta (H. A. Crum and L. E. Anderson 1981), or because an innovation originatedproximally and developed beyond the perichaetium (Chen P. C. et al. 1963), in some species ofArchidium originally included in the genus (J. A. Snider and W. D. Margadant 1973). Rhizoidaltubers were reported for the genus by T. Arts and S. Risse (1988). The “central accessory cells”as used here are equivalent to Begleiter or hydroid cells of other authors.

SELECTED REFERENCES Bryan, V. S. 1956. Chromosomes and systematic position of the inoperculate mosses, Pleuridium andBruchia. Amer. J. Bot. 43: 460–468. Snider, J. A. 1994b. Pleuridium. In: A. J. Sharp et al., eds. The moss flora of Mexico.Mem. New York Bot. Gard. 69: 92–95.

1. Fertile plants capitate, julaceous proximal to abruptly enlarged and spreading perichaetialleaves; sterile plants julaceous throughout, bearing short, appressed, blunt leaves; cells atshoulder of perichaetial leaves rhombic; costa in transverse section showing a single extensiveabaxial stereid band and adaxial guide cells . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4. Pleuridium sullivantii

1. Fertile plants erect-patent proximal to gradually differentiated perichaetial leaves; sterileplants with leaves erect-patent, erect to flexuose-spreading; cells at shoulder of perichaetialleaves linear; costa in transverse section with a wider abaxial stereid band, a narrow adaxialstereid band, and central guide cells.2. Perichaetial leaf lamina in transverse section uniformly 1-stratose at shoulder; plants

autoicous, antheridia enclosed in leafy buds in axils of stem leaves . . . . . . . . . . 3. Pleuridium subulatum2. Perichaetial leaf lamina in transverse section at least partly 2-stratose at shoulder; plants

paroicous, antheridia in axils of stem leaves naked or subtended by a membranousbract.

Pleuridium

464 DITRICHACEAE

[3. Shifted to left margin.—Ed.]3. Shoulders of perichaetial leaves with jagged teeth; leaf lamina in transverse section 2-stratose

on either side of costa, 1-stratose towards margin, plicate at the transitional area . . . . 1. Pleuridium ravenelii3. Shoulders of perichaetial leaves uniformly serrulate but never jagged; leaf lamina in trans-

verse section sporadically to completely 2-stratose leaving the margin narrow and 1-stratose,concave, plicae absent . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2. Pleuridium acuminatum

1. Pleuridium ravenelii Austin, Bull. Torrey Bot. Club 6:142. 1877

Stem leaves erect, concave, laminajuxtacostally 2-stratose, becoming1-stratose towards margin;proximal leaves minute, bract-like,narrowly deltoid, acuminate,0.53–0.85 × 0.15–0.25 mm,entire; distal stem leaves ovate tolanceolate, acuminate to subulate,1.05–1.75 × 0.2–0.38 mm, entire;

costa broad, percurrent to excurrent. Sexual conditionparoicous, antheridia naked in the distal leaf axils justproximal to the perichaetium. Perichaetial leaves oblongto obovate-lanceolate proximally, carinate-acuminatedistally, gradually narrowed to a broad, channeled tosubtubulose acumen which is generally shorter than theleaf base, 1.58–2.63 × 0.43–0.58 mm, margins serrulateto serrate, erect to incurved distally, coarsely andirregularly to distinctly jaggedly toothed at shoulder;lamina plicate to pleated; basal cells oblong torectangular; median cells subquadrate to short-rectangular; distal cells at shoulder longer, long-rhomboidal to curved linear; costa excurrent with aconduplicate or canaliculate awn, broad, smooth on back,indistinct at mid leaf, confluent with the juxtacostal partof lamina, filling most of the acumen; transverse sectionof costa at mid leaf with adaxial guide cells and abaxialstereid cells forming wide rows across the width with thecentral accessory cells forming an aperture; innermostperichaetial leaves ovate-acuminate, percurrent. Seta0.15–0.2 mm. Spores (32–)37.5–42.5 µm, bluntly andfinely papillose, yellow to orange in mass.

Capsules mature Mar–Jun. Bare sandy soil, openspaces of scrub oak association; low to moderateelevations; Ala., Ark., Del., Fla., Ga., La., Mass., Mo.,N.J., N.C., Okla., Pa., R.I., S.C., Tex., W.Va.

The chromosome number of Pleuridium ravenelii isn = 13 (North Carolina, H. A. Crum and L. E. Anderson1981). The species is characterized by (1) plicate leaflamina (most easily observed in transverse sections), (2)lamina outwardly 1-stratose but 2-stratose on either sideof the costa, (3) channeled distal portion of costa, and(4) coarsely toothed shoulder. Serrations of the leafshoulder, however, vary from minimally toothed withprojecting ends of marginal cells to abruptly exaggerated(“jagged shoulders,” Crum and Anderson ). Though notalways obvious because of the plicate lamina and the

canaliculate costa, the jaggedly toothed shoulders aremost pronounced in outer perichaetial leaves. The sporesare the largest in the genus, as initially described byAustin. Early American bryologists (e.g., S. Watson inW. H. Brewer et al. 1876–1880, vol. 2; C. L. Lesquereuxand T. P. James 1884) considered P. ravenelii a taxonintergrading with P. acuminatum because of theintermediate leaf shape. Crum and Anderson suggestedthat P. ravenelii is an extreme habitat response of P.acuminatum populations along the coastal sand dunesof eastern North America. Most specimens examinedare, indeed, from such characteristic habitats of thesoutheastern Coastal Plain. An occasional specimen mayresemble P. acuminatum or P. subulatum in general habit.For instance, a specimen from Florida (Breen 2930, NY)has an ovate-lanceolate leaf base with narrowlyacuminate tips and is 1-stratose in the portion of thelamina towards the margins (and is therefore close to P.subulatum), but (1) the carinate acumen (clearest in thecharacteristic transverse section), (2) the jagged teeth atleaf shoulders (usually obscure because hidden by theconduplicate costa and the plicate lamina), and (3) thejuxtacostally 2-stratose leaf lamina support itsidentification as P. ravenelii.

2. Pleuridium acuminatum Lindberg, Öfvers. Kongl.Vetensk.-Akad. Förh. 20: 406. 1863

Pleuridium bakeri Cardot &Thériot; P. bakeri var. elongatumCardot & Thériot; P. bolanderiA. Jaeger; P. californicum Grout;P. stramineum Austin

Stem leaves patent-erect,spreading, concave, occasionallyplicate, lamina 2-stratose distally(appearing multistratose in

extreme forms), 1-stratose at base; proximal leaves ovateto deltoid, long-acuminate, 0.18–1.1 × 0.1–0.28 mm,entire proximally, serrulate distally; distal stem leavesdeltoid to ovate, long-acuminate, 0.58–1.88 × 0.15–0.35mm, entire proximally, serrulate distally