OF WESTERN PEXXSYLVAXIA 107 







undivided or cleft or cribrose, rarely divided to the base into 

 filiform parts, trabeculae mostly projecting only outwards; 

 operculum mostly rostrate, sometimes deciduous with the at- 

 tached columella ; calyptra mostly small, mitrate or cucullate, 

 glabrous, sometimes campanulate and plicate. 



A large family, world-wide in distribution, but most abun- 

 dant in sub-arctic and temperate regions, mostly on stones or 

 rocks, rarely on soil or trees. 



Key to the Genera. 



a. Costa with basal guides, or homogeneous; calyptra rarely cam- 

 panulate; spores small to medium-sized, b. 



a. Costa with several median guides; spores small; calyptra campanu- 

 late. i. Glyphomitrium. 

 b. Teeth undivided, cribrose, cleft in upper half, or none; branches 



as high as the stem. 2. Grimmia. 



b. Teeth divided almost to the base into two filiform divisions; 

 branches irregular and short. 3. Rhacomitniun. 



1. Glyphomitrium R ridel. 

 ( Ptychomitrium Fuernrohr). 



Autoicous: cespitose in loose yellowish-green to brownish 

 or blackish cushions; stem with central strand, erect or ascend- 

 ing, radiculose at the base, thickly-leaved ; leaves long, narrow, 

 the points not hyaline, crispate when dry, spreading when 

 moist ; costa strong, percurrent or ending below the apex ; cells 

 not with sinuose walls, smooth, upwards small and rounded- 

 quadrate, below linear to more or less loosely rectangular; 

 perichsetial leaves not sheathing: seta straight, more or less 

 elongate, mostly two or more to a perichaetium ; capsule 

 smooth, erect, symmetric, mostly oval to oblong-elliptic ; 

 annulus wide, deciduous, rarely none ; peristome inserted be- 

 low the mouth ; teeth papillose, usually deeply divided into two 

 subulate prongs, trabeculae more or less distinct; spores small; 

 operculum conic with a long, fine, straight beak ; calyptra 

 campanulate, plicate and lobed. 



A widely distributed genus of 66 species, of which at least 

 9 occur in North America and one in our region. Occurring 

 on rocks and stones, rarely on trees. 



1. Glyphomitrium incurvum (Schwaegrichen) Brotherus. 

 (Ptychomitrium incurrnui Sullivant). 



Densely cespitose, dark green to brownish : stems about 5 

 mm. high, erect ; leaves erect-spreading when moist, sometimes 

 incurved, twisted-crispate when dry, the lower small, increas- 

 ing in size upwards, linear-lanceolate, obtuse, thick, opaque, 

 the margin plane; costa broad, ending in apex; basal leaf- 

 cells rectangular, pellucid, the upper much smaller, rounded to 

 quadrate, incrassate, dense; seta about 3-4 mm. high, erect; 



