OF WESTERN PENNSYLVANIA 107 



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

 filiform parts, trabeculse 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. Grimnda. 



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

 branches irregular and short. 3. Rhacomitrium. 



1. Glyphomitrium B ridel. 



{Ptychoinitrium 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 r^.unded- 

 quadrate, below linear to more or less loosely rectangular; 

 perichaetial 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, trabeculas 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. 

 (Ptychomitriuin incurvum Sullivant). 

 Densely cespitose, dark green to brownish : stems about 5 

 mm. high, erect ; leaves erect-spreading when mdist, 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 Z-A mm. high, erect; 



