OF WESTERN PENNSYLVANIA 101 



emergent, obtusely apiculate, cleistocarpous ; calyptra cucul- 

 late, conic, covering only the upper portion of the capsule ; 

 spores large, .028-.035 mm., yellowish-pellucid, finely rough- 

 ened, mature in spring: autoicous or paroicous, antheridia clus- 

 tered in the axils of the upper leaves. 



On soil in old fields, pastures, etc., usually preferring a 

 sandy soil, in Europe, Asia, Algeria, South America, and from 

 Ontario to the Carolinas and west to the Pacific States. Rarely 

 found in our region. 



Reaver : T. P. James. (Porter's Catalogue). 



10. POTT I A Ehrhart, Fuernrohr. 



Autoicous or paroicous, rarely synoicous or dioicous : 

 small, gregarious to cespitose, green to brownish or whitish : 

 stem with central strand above, often simple, radiculose at 

 base, leafy ; leaves tufted above, spreading to imbricate, cari- 

 nate to deeply concave, oblong to elongate-lanceolate, or spatu- 

 late. acuminate to piliferous, rarely obtuse, margin revolute or 

 plane ; costa without lamellae, complete to excurrent, rarely in- 

 complete ; lower leaf-cells elongate, pellucid, smooth, the upper 

 rounded-quadrate or rounded-hexagonal, mostly papillose on 

 both sides : seta mostly long and straight ; capsule exserted 

 or rarely immersed, erect, symmetric, short-necked ; annulus 

 none or deciduous or remaining attached ; peristome often none 

 or rudimentary, when present of 16 perforate or upwards 2-3- 

 cleft teeth upon a basal membrane, articulate ; operculum 

 mainly obliquely rostrate, rarely conic-obtuse, sometimes not 

 deciduous ; calyptra cucullate, papillose or smooth, usually fall- 

 ing away with the operculum ; spores large, variously papillose 

 or pitted. 



A genus of about 62 species widely distributed, on soil or 

 soil-covered rocks, mainly in the temperate zones ; 12 species 

 in North America, 1 species in our region. 



1. Pottia truncata [ Iledwig] Fuernrohr. 

 (P. truncatula Lindberg : Gymnostomum truncatnin Hedxvig). 



(Plate XIII) 



Densely cespitose, dull green : stems simple or sparingly 

 branched, erect, about 2.5 mm. high, radiculose at base; leaves 

 numerous, the upper much larger than the lower, obovate to 

 oblong-spatulate, about 1.5-2.5 mm. long, soft, spreading, the 

 margins plane, minutely crenulate with the projecting trans- 

 verse cell-walls, the leaves when dry become twisted, apex 

 abruptly acute, costa strong and excurrent into a short point ; 

 basal leaf-cells quadrate to rectangular, large, lax, hyaline, 

 more or less inflated, above becoming gradually smaller, the 

 median and upper medium- to thin-walled, smooth, hexagonal : 

 seta erect, about 3-4 mm. high, mostly yellowish : capsule 



