Donnell's Archidium Moss

Archidium donnellii usually can be distinguished from other species by irregular areolation in median and distal portions of lamina, proximal lamina cells not strongly differentiated, and sexuality autoicous. It tends to grow in drier habitats than do other species of the genus.

Plants 2-10 mm, perennial, in dense turfs, yellow-green. Stems simple or usually branched by several sterile innovations, becoming prostrate with age. Stem leaves erect to erect-spreading, lanceolate to narrowly ovate-lanceolate, acuminate, 1-2.5 mm; costa percurrent or short-excurrent, sometimes somewhat subulate; laminal margins recurved, smooth or finely serrulate distally; median and distal laminal cells irregular in shape, mixed quadrate, trapezoidal, short-rectangular, short- to long-rhomboidal, 14-75 × 8-13 µm, proximal cells quadrate to short-rectangular, similar to median and distal cells; leaves of innovations similar to stem leaves, not much reduced proximally. Perichaetial leaves broadly ovate-lanceolate, narrowly acuminate to subulate, sometimes flexuose to secund, same size as stem leaves; costae short to long excurrent, hairpoint pellucid, sometimes finely spinose; laminal margins recurved, smooth to finely serrulate; distal and median laminal cells similar to stem leaves, proximal laminal cells lax, wider, rectangular, 2-4:1, 35-115 × 12-25 µm, sometimes somewhat hyaline. Specialized asexual gemmae absent. Sexual condition autoicous; antheridia terminating axillary leaf buds. Capsule terminal, 425-750 µm. Spores typically 28(4-60) per capsule, angular to irregularly polyhedral, 120-230 µm, smooth or finely granulose, yellow to orange-red.

Archidium ohioense var. donnellii (Austin) Lesquereux & James

Archidium donnellii Aust. Bull. Torrey Club 6 : 190. 1877
Archidium ohioense Donnellii Lesq. & James, Man. 50. 1884.
Plants gregarious in yellow masses; stems seldom more than 5 mm. high, branching by
subapical innovations, bearing small leaves: fruiting plants usually leafless below or with
short rudimentary bracts, capitate, the upper leaves crowded, longer, lanceolate or subulate,
up to 2 mm. long; costa terete, percurrent or excurrent into a smooth subulate awn; margins
finely serrulate below; basal cells oblong, rectangular, 27-40 ju long by 13 m wide, soon becoming
narrowly prosenchymatous, 67-81 m long by 8-10 m wide; alar cells often hyaline. Autoicous:
antheridia terminal on a slender branch: capsule immersed, 250 m in diameter; cells of walls
hexagonal, 27 m in diameter: spores large, angled, 120-164 ju in diameter, maturing in April.
Type locality: Hampden County, Virginia. Distribution: Maryland to South Carolina.