OF WESTERN PENNSYLVANIA 113 



acuminate, apex hyaline, denticulate, margin more or less bi- 

 stratose above, usually revolute below ; costa strong, ending 

 in apex; basal leaf-cells linear, sinuose, incrassate, upper leaf- 

 cells rounded-quadrate : seta short, light-colored, often curved 

 or flexuose ; capsule relatively very small, elliptic, pale brown, 

 thin-walled; annulus large, revoluble; peristome-teeth brown- 

 ish, irregularly divided; lid conic-rostrate, shorter than the 

 urn ; spores mature in spring. 



On wet rocks or cliffs, principally granite or gneiss, Eu- 

 rope. Asia, and, in North America, from Greenland to British 

 Columbia, south to Oregon and northeastern United States. 

 Perhaps to be expected in the eastern or northeastern part of 



our region. 



3. Rhacomitrium ericoides (Schwaegrichen) Xew Com- 

 bination. 



(Trichostonmm ericoides Schwaegrichen; Dicrannm microcarpum 

 Schrader). 



Cespitose in low, green to yellow-green tufts : stems 

 slender, markedly nodose with obtuse lateral innovations ; 

 leaves crowded, spreading to falcate-secund, lanceolate from an 

 ovate base, acuminate, the apex hyaline, flat, denticulate, not 

 very narrow, margin revolute, not thickened ; costa strong, 

 ending in the apex; leaf-cells all linear, the upper 3-6:1, in- 

 crassate, sinuose, the marginal shorter and in the alar portion 

 often a few larger, rectangular, pellucid, and not sinuose- 

 walled : seta yellowish, short; capsule small, elliptic-cylindric 

 to oblong, pale yellow-brown, thin-walled ; annulus large, 

 revoluble; peristome-teeth short, divided almost to the base; 

 calyptra somewhat papillose at the apex; lid short-rostrate; 

 spores mature in spring. 



On exposed rocks and stones in hilly or mountainous re- 

 gions, Europe, and, in Xorth America, from Greenland to Brit- 

 ish Columbia south to Oregon and eastern Pennsylvania. Per- 

 haps will be found in the eastern part of our region. 



Family VIII. ORTHOTRICH ACEAE. 



Dioicous or autoicous, rarely heteroicous or polyoicous : 

 cespitose, light green to yellowish- or blackish-green outside 

 the tufts, inside brown to black : stem mostly with no central 

 strand, erect to ascending, or creeping with erect or ascending 

 branches, radiculose below, or along the creeping stem, with 

 reddish or brownish filaments ; leaves spreading to squarrose, 

 carinate, mostly from a decurrent base more or less lanceo- 

 late, sometimes oblong-lingulate to linear, mostly entire, 

 usually papillose both sides : costa strong, sometimes excur- 

 rent-aristate or piliferous; upper cells generally rich in chloro- 

 phyll, round-quadrate to round-hexagonal, basal mostly elon- 



