Denuded Dicranodontium Moss

Sporophytes of Dicranodontium denudatum are rare in North America, and the season when capsules are mature is unknown. This species is more widespread in the flora area than the other two. It is recognized by the setaceous, erect-flexuose to falcate-secund leaves with auriculate bases with inflated, hyaline or sometimes reddish alar cells. The leaves are commonly deciduous leaving the stems often partially denuded, and revealing scars and whitish remnants of leaf bases that are very characteristic of the species. The cells above the alar region and adjacent to the costa are narrowly rectangular, hyaline or sometimes reddish.

At first glance this species is easily confused with sterile plants of species in other genera; e.g., Dicranella heteromalla, Paraleucobryum longifolium, Ditrichum crispatissimum, D. flexicaule, D. pallidum, Dicranum fulvum, and Campylopus spp. The distinctive features noted above, however, will aid in recognizing D. denudatum. In addition, it differs from all of the above except Campylopus spp. by the usual occurrence of rhizoids on the abaxial surface of the costa. It is easily distinguished from Campylopus by its costa smooth in the mid leaf region compared to the costa of the latter having ridges or lamellae.

Plants small to rather large, 1–3(–5) cm high, deep green to yellowish green, in slightly silky, dense tufts. Stems erect or ascending, simple or sparsely branched, densely foliate above, radiculose below; central strand present. Leaves distinctly deciduous in sections, flexuose or falcate-secund when dry, erect-spreading when moist, linear-lanceolate, 2.5–5.0(–8.0) mm long, gradually tapered from an oblong-ovate, not clearly sheathing base to a long, setaceous, semi-canaliculate acumen; margins plane or slightly incurved above, entire below or serrulate in the upper half or only at the apex; costa pellucid, poorly delimited at leaf base, occupying 1/3– ½ the leaf base width, long-excurrent, smooth at back; upper cells long-rectangular, linear near the apex; lower cells rectangular, 18–30 µm × 4–8 µm, firm-walled, becoming shorter and narrower towards the margins, not forming clear marginal bands; alar cells forming somewhat auriculate base, short-rectangular to quadrate, inflated, hyaline or sometimes reddish brown. Dioicous. Setae flexuose when dry, cygneous when moist, 5–10 mm long, yellowish; capsules suberect to slightly inclined, cylindric, 1.0–1.2 mm × 0.5–0.6 mm, yellowish brown; opercula long-rostrate, slightly shorter than the urns; annuli absent; peristome teeth lanceolate, ca. 0.2 mm long, divided about to the middle, vertically striate and reddish. Calyptrae ca. 1.5 mm long, entire at base. Spores 10–14 µm in diameter.

Plants yellowish brown to dark green, glossy, in loose to dense tufts. Stems 2-4(-8) cm, radi-culose proximally with reddish brown rhizoids. Leaves erect-flexuose to falcate-secund, spreading at ca. 30º, 3-8 mm, often deciduous, setaceous, auriculate at base, subtubulose to tubulose throughout, margins entire proximally, serrulate near apex, apex acute; costa indistinct, occupying ca. ¹/3-¹/2 of leaf base; cells not thick-walled or pitted, distal cells rectangular to linear, 24-47 × ca. 7 µm, basal cells 9-14 µm wide, alar cells usually forming auricles, hyaline or reddish. Seta 8-12 mm, curved or cygneous. Capsule 1.6-2 mm, oblong-cylindric, erect; opercula about as long as capsule. Spores 10-15 µm.

Distribution: China, Nepal, India, Japan, Russia, Europe, and North America.

Habitat: on rotten logs and soil or thin-soil over rocks.

Dicranodontium longirostre (Web. & Mohr) Bruch & Schimp. in B.S.G., Bryol. Eur. 1: 158. (fasc. 41. Mon. 2.1). 1847. Swartzia longirostra (Web. & Mohr) Brid. in Röhl., Ann. Wetterauischen Ges. Gesammte Naturk. 3(2): 203. 1814. Didymodon longirostre Web. & Mohr, Bot. Taschenb. 155. 1807. Dicranodontium uncinatulum C. Müll. in Jaeg., Ber. Thätigk. St. Gallischen Naturw. Ges. 1877–78: 381. 1880.

Dicranum denudatum Bridel, Muscol. Recent., suppl. 1: 184. 1806; Dicranodontium millspaughii E. Britton; D. virginicum E. Britton