Ohio Archidium Moss

Archidium ohioense is the most widespread and variable species in the genus. J. A. Snider (1975) assigned many names to the synonymy of this species. In the United States, the plants vary from rather tall, lax, weakly branched forms with longer leaves in wet sites to short, strongly branched forms with shorter leaves in drier sites. The perichaetial position is also highly variable. Future work may show the species to consist of a series of closely similar species, as suggested by the rather anomalous and scattered world distribution. Archidium ohioense is most easily confused with A. alternifolium and A. tenerrimum, but can be distinguished from them by a combination of primarily lateral capsules, antheridia enclosed in leafy bracts, and sexuality autoicous.

This species was reported from Jiangsu (Z.-L. Liu et al. 1989) and Zhejiang provinces (D.-K. Li and C.-H. Gao 1983), but the authors could not confirm these reports.

Plants 2-20 mm, perennial, sometimes gregarious but mostly in dense short turfs, green to yellow-green. Stems variable, simple, with few innovations, or often short and multi-branched by numerous innovations from axils of stem leaves or exterior perichaetial leaves, often becoming prostrate with age, innovations fragile and often detached. Stem leaves erect to erect-spreading, lanceolate, triangular or ovate-lanceolate, narrowly acuminate to subulate, 0.5-2 mm, becoming reduced proximally; costa percurrent to distinctly excurrent in hairpoint; laminal margins plane, smooth or finely serrulate distally; median laminal cells rhomboidal to prosenchymatous, 4-8:1, 45-90 × 9-15 µm, somewhat shorter distally and along margin, proximal cells short-rectangular to rectangular, 2-4:1, 25-60 × 12-16 µm, short-rectangular to quadrate in alar region in 2-6 rows extending 6-15 cells along proximal lamina margin; leaves of innovations similar to distal stem leaves except smaller, often sharply reduced proximally. Perichaetial leaves variable in shape, ovate, oblong, ovate-lanceolate to lanceolate, larger, 1-2 mm, short- to long-acuminate; costa percurrent to long-excurrent, often forming pellucid hairpoint; laminal margins smooth, plane or rarely weakly recurved; median laminal cells rhomboidal, linear-rhomboidal to prosenchymatous, 4-8:1, 45-140 × 9-15 µm, shorter distally and along margin, proximal cells hyaline, lax, rectangular to rhomboidal, 4-6:1, 50-90 × 12-18 µm. Specialized asexual reproduction absent. Sexual condition autoicous, antheridia terminating axillary leaf buds. Capsule lateral, or both lateral and terminal, 270-600 µm. Spores typically 16(4-60) per capsule, rounded-triangular to polyhedral, 110-320 µm, pale yellow, smooth to papillose.

Plants gregarious to loosely tufted, 2–30 mm high, yellowish green to green, not glossy. Stems erect, simple or 2–3-branched by subapical or lateral innovations. Upper stem leaves erect-spreading to spreading, channelled, ovate-lanceolate or lanceolate to narrowly long-triangular, acuminate to subulate, 0.5–1.7 mm × 0.16–0.28 mm wide; margins entire to faintly serrulate above; costa percurrent to strongly excurrent; median cells rhomboidal to prosenchymatose, 45–90 µm × 9–14 µm, shorter toward the apex; basal cells short-rectangular to rectangular, those at alar regions quadrate in 2–6 rows. Autoicous; perichaetia and perigonia mostly lateral and sessile, occasionally terminal on short branches. Perichaetial leaves 1–2 mm long, ovate, oblong-ovate, ovate-lanceolate, or lanceolate, short- to long-acuminate; margins plane, entire to faintly serrulate above; costa percurrent to strongly excurrent; median cells rhomboidal to prosenchymatose, 45–140 µm × 9–14 µm, shorter above; basal cells loosely rhomboidal to rectangular. Rhizoids smooth, rhizoidal tubers present. Capsules lateral or occasionally terminal, about 0.4 mm broad. Spores 4–60, often 16, per capsule, 110–310 µm, irregularly angled, smooth to densely papillose.

Distribution: China, India, Sri Lanka, Japan, New Caledonia, Africa, West Indies, and North America.

Habitat: on rocks or sandy soil.

Archidium floridanum S. A. Cain

Archidium sinense Durieu in Debeaux, Bull. Soc. Bot. France 9: 161. 1862. Type. China: Shandong, Yan-tai near Teché-fou, Debeaus s.n., 1861.

Archidium ohioense Schimp.; (B.S.G. Bryol. Eur. (43:) Archid ed. 2. 3 ; hyponym. 1850) C. Miill. Syn. 2 : 517. 1851.
Plants seldom more than 5-10 mm. high, branching by repeated subapical innovations, varying from light-yellow to black: leaves narrowly lanceolate-subulate, seldom 1 mm. long; costa excurrent or ending in the subulate awn ; margins serrulate ; basal cells oblong, becoming rhomboidal or hexagonal, 13 ^ wide by 27-54 m long; perichaetial leaves longer and broader, 1-1.5 mm. long. Autoicous or cladautoicous : antheridia on basal stems or in axillary buds, with 3-4 ecostate bracts: calyptra small, fugacious: capsule sessile in axillary buds, 1-8 on a single plant, seldom more than 25-33 ^ in diameter; walls thin, the cells hexagonal, 27 by 54 m: spores few, 12-24, angled, large, 135-162 /i in diameter, smooth, the contents yellow or brown and filled with oil-globules, maturing from September to April.
Type locality; Harper's Ferry, Virginia.
Distribution: In wet fields or bare places in dry soil from Quebec and New York to Minnesota, Florida, and Louisiana.