Archidium
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Authority
Sharp, Aaron J., et al. 1994. The Moss Flora of Mexico. Part One: Sphagnales to Bryales. Mem. New York Bot. Gard. 69 (1): 1-452.
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Family
Archidiaceae
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Scientific Name
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Description
Genus Description - Small mosses (up to 20 mm high), usually perennial, gregarious to tufted, on moist soil in disturbed habitats. simple or forked because of innovations that often become prostrate stolons producing erect branches the following year. Leaves larger and more crowded above, sometimes in capitate clusters, erect to erect-spreading, occasionally ± secund, scarcely altered on drying, elongate, oblong or ovate to lanceolate, occasionally long-triangular, obtuse, acute, or acuminate; margins plane or narrowly recurved on 1 or both sides above the shoulders, entire to serrulate; costa subpercurrent to strongly excurrent, consisting of homogeneous, thick-walled cells; upper cells short to moderately elongate, quadrate to rhomboidal; basal cells thin-walled, subquadrate or short-rectangular, those at the margins often short and subquadrate. Monoicous. Perichaetial leaves somewhat longer than vegetative leaves and sheathing at base. Setae none; capsules terminal or lateral, deeply immersed, small (200-750 µm in diameter), globose, pale-yellow, indehiscent except by rotting or irregular rupture; exothecial cells in 1 layer, transparent, hexagonal, lax and thin-walled below, rather firm-walled above; stomata, peristome, and columella none. Spores usually few but variable in number (4-176 per capsule), rounded to irregularly tetrahedral, large (50-310 µm), pale to orange-yellow, very thick-walled, smooth or minutely roughened, maturing in late fall to early spring. Calyptrae evident only as a torn membrane attached to the vaginula. The plants are characterized most significantly by embryonic capsules, as seen in section, originally of 2 cells (never forming a quadrant); sporogenous cells not organized into an archesporium, the inner cells of the endothecium potentially sporogenous (the spore mother cells 1-44 per capsule), the remaining endothecial cells serving as nutritive cells that become completely resorbed as spores mature; columella lacking; amphithecium of 3 layers of cells, the 2 inner layers resorbed resulting in a single-layered capsule wall.