OF WESTERN PENNSYLVANIA 129 



spores large, papillose, mature in late autumn to early spring. 

 On moist earth, often in swamps, eastern North America. 

 Occurs in Central Ohio and Eastern Pennsylvania and is, prob- 

 ably, the plant referred to aS follows: 



Indiana : James. (Porter's Catalogue). 



2. ACAULON C. Mueller. 

 (Sphaeraiigium Schimper). 



Dioicous : minute, bud-like, brown, gregarious : stem very 

 short and few-leaved, without central strand, unbranched, 

 green protonema persistent; leaves erect-spreading, broadly 

 ovate, keeled or concave, above with revolute and sinuate- 

 denticulate margin, or plane and entire ; costa more or less ex- 

 current-cuspidate ; upper cells short-rhombic, below rhom- 

 boidal, dorsally strong thickened, smooth, rarely with a few 

 high papillae, the lowest thin-walled, hyaline and rectangular: 

 seta very short ; capsule sub-globose, cleistocarpous, immersed ; 

 calyptra very small and delicate, conic-mitriform 3-5-cleft; 

 spores small, brown, subglobose, minutely granulose. 



A widely distributed genus, on soil, mostly in the temper- 

 ate zone. Fifteen species in all, 4 in North America, 2 in our 

 region. 



Key to the Species. 



a. Uppermost and perichastial leaves sharply carinate and with re- 

 flexed margins. i. .-J. triquetniin. 

 a. Uppermost and perichjetial leaves concave; and with margins plane. 



2. .1. rufcscens, 



1. Acaulon triquetrum (Spruce) C. Mueller. 

 (Sphaeranginiii triquetniin Schimper). 



Plants minute, about 1 mm. high, bulbiform, pale green 

 or yellowish, distinctly triquetrous; protonema green, persist- 

 ent; lower leaves small, rounded, the middle leaves larger, 

 broadly ovate, deeply concave, convolute, the upper largest 

 (perichsetial) broadly ovate, deeply carinate, triquetrous, all 

 upper leaves with reflexed margins, erose-denticulate above; 

 costa strong, in upper leaves excurrent in a recurved apiculus ; 

 basal leaf-cells elongate-hexagonal, lax, thin-walled, hexagonal 

 to oblong-hexagonal: seta about as long as capsule, arcuate; 

 capsule globose, smooth; calyptra minute, mitrate, cleft-lobed, 

 covering only very apex of capsule ; spores papillose, about 

 .025-.030 mm., mature in early spring. 



On clayey or sandy soil in fields or on banks, Europe, 

 Algeria, and, in North America, from western Canada to 

 New England south to the Carolinas ; occurs in Ohio and in 

 Pennsylvania but not yet reported from our range. 



