Riccia mcallisteri

Riccia mcallisteri M. A. Howe, Bryologist 20: 35. 1917
Thalli medium-sized, 5-8 mm. long, 2 or 3 times rather divergently forking, often forming densely gregarious more or less radiating masses, regularly reticulate above, bright-green when living, often whitish-green or yellowish-green with age or on drying, violet-purple or sometimes decolorate at margins and on sides; main segments oblong or oblong-obovate, 1.52.5 mm. wide; terminal segments ovate, subquadrate, or somewhat obcordate, roundedobtuse or subacute; margins acute, ascending, their edges hyaline or violet and unistratose for a width of one or two cells; median sulcus acute and sharply defined in anterior parts, becoming obscure* in the posterior; scales entire, reddish-violet, claret-colored, or sometimes decolorate, imbricate, slightly exceeding the margins; transverse sections of the thallus mostly 2-3 times as broad as high, 1 8-25 cells thick in median parts, the ventral outlines rounded-convex or occasionally somewhat flattened; dorsal epidermis of two (or three) layers of cells, the cells of the primary stratum mostly mammiform-apiculate, soon collapsing and leaving rather inconspicuous vestiges, the cells of the secondary superficial stratum mostly 26-78 /x broad, these and the underlying cells in very distinct and regular rows when viewed from above. Monoicous; antheridial ostioles elevated 50-160 ju, often violet; capsules usually numerous, soon exposed, the spores lying in long conglobate masses at the bottom of a deep widely open pit or trough; spores at first violet or violet-brown, soon violet-black and opaque, 78-132 ju in maximum diameter, ellipsoid, ovoid, subspheric, or obscurely tetrahedral, wholly destitute of wing-margins, at first almost uniformly areolate over the whole surface, the areolae mostly 7-15 }x in diameter, soon obscure, and the spores finally appearing densely echinulate, the spinulae 5-1 1 /x long, truncate or obtuse, or occasionally subacute, sometimes cristate-furcate.
Type locality: Granite Mountain, Texas. ' Distribution; Missouri, Nebraska and Texas.