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FNA | Family List | FNA Vol. 27 | Ditrichaceae

3. Ditrichum Hampe, Flora. 50: 181. 1867.

[Greek di-, two, and trichos, 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 brown proximally. 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; margins entire throughout or denticulate near the apex; costa percurrent or excurrent, occupying most of subula, 1/6-1/3 width of leaf base, 1 row of guide cells, 2 stereid bands, adaxial stereid band sometimes weak, rarely absent; medial lamina cells quadrate to short-rectangular, becoming longer and thinner-walled proximally toward margins, smooth or rarely papillose at both ends. Specialized asexual reproduction occasionally by rhizoidal tubers. Sexual condition monoicous or dioicous; perichaetial leaves usually with a longer and more or less sheathing base and shorter subulate 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 to cylindric, smooth; annulus present, deciduous; operculum conic to short-rostrate; peristome single, teeth16, split into 2 filiform segments or sometimes irregularly perforate or split, with or 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)
+ Plants loosely to densely tufted or gregarious; stems, if tomentose, only so at extreme base   (3)
       
2 (1) 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 nodulose longitudinal walls; plants commonly fruiting.   2 Ditrichum flexicaule
+ Stems to 7 cm or more; leaves from an elongate-ovate base tapering gradually to the long slender subula; costa abaxially weakly convex; basal laminal cells with weakly to strongly nodulose longitudinal walls; rarely found fruiting   3 Ditrichum gracile
       
3 (1) In cross section, distal leaf lamina partially 1-stratose with 2-stratose margins   (4)
+ In cross section, distal leaf lamina 2-stratose from costa to margins   (8)
       
4 (3) Leaves erect-appressed to erect-patent when moist   (5)
+ Leaves erect-spreading when moist   (6)
       
5 (4) Leaves oblong-lanceolate, widest proximally to middle, tapering to a blunt apex; lamina cells thin-walled, rectangular throughout, slightly shorter and narrower towards apex; seta to 2.5 cm, yellowish to orange-brown, erect; peristome teeth 200-220 µm, perforate, divided into 2 adhering filaments, finely papillose.   5 Ditrichum lineare
+ Leaves lanceolate to linear-lanceolate, gradually acuminate; lamina cells ± incrassate, subquadrate to short-rectangular distally, elongate-rectangular proximally; seta to 1.5 cm, reddish with age; peristome teeth 200-250 µm, the filaments finely and obliquely ridged and lightly papillose.   8 Ditrichum pusillum
       
6 (4) 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
+ Stem branching distally from base; leaves lanceolate to linear-lanceolate, margins entire to serrulate distally, apex weakly toothed; seta shorter, 0.8-2 cm, red to orange-brown; capsule symmetric to slightly curved, 1-3 mm, not flattened when dry; peristome teeth 200-500 µm, papillose to spiculose; dioicous   (7)
       
7 (6) 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; capsule usually symmetric, straight and erect, rarely curved, 1.5-3 mm long, dark brown to reddish; peristome teeth 200-500 µm, twisted when dry.   1 Ditrichum ambiguum
+ Stems to 0.5 cm, seldom branched; leaves 1-3 mm, apex serrulate, margins plane or narrowly recurved from above leaf base to leaf middle; leaf cross section 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
       
8 (3) Stem leaves 1.5-3 mm, from an ovate to oblong base gradually tapered to a channelled subula, erect-patent to subsecund; dioicous.   4 Ditrichum heteromallum
+ Stem leaves longer, 3-7 mm, long-subulate from an ovate to short-rectangular base, spreading, flexuose to subsecund; autoicous   (9)
       
9 (8) 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; spores yellow-brown, 11-19 µm, vermicular papillose-verrucose   9 Ditrichum rhynchostegium
+ Leaves 3-7 mm; seta 1-3 cm, yellow or becoming reddish brown at the base when mature; capsules subcylindric to cylindric, not flattened when dry; peristome teeth to 800 µm, finely papillose to spiculose-papillose; spores brown, 15-30 µm, coarsely roughened-papillose   (10)
       
10 (9) 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
+ Leaves narrow filiform-subulate from an ovate-lanceolate sheathing base; seta 1-3 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

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