GRIMMIACEAE 37 



H. albicans (Web.) Linrib. (II. ciliata Ehrh.) On rocks, 

 frequent. Spring. 



CAMPYLOSTELIUM B. & S. 



Plants minute, gregarious, on rocks. Leaves crisped when 

 dry, linear-lanceolate; leaf cells above small, round, thick- 

 walled. Calyptra mitrate; seta arcuate; capsule symmetric. 



C. saxicola (Web., Mohr.) B. & S. "On sandstone boulders 

 near Closter, N. J.," Muse. App. 109. Winter-spring. 



PTYCHOMITRIUM B. & S. 



Distinguished from Grimmia by the plicate calyptra and 

 crispate leaves. 



P. incurvum (Schwaegr.) Sulliv. New Dorp, S. Id., and Bronx 

 Park, E. G. B. (Bx.)!; "Old stone fences, Northern N. J. and 

 Southern N. Y.," Muse. App. 153; Yonkers, Bx! 



GRIMMIA Ehrh. (Plate III, Fig. 2.) 



Plants dark green to almost black, short-stemmed, growing 

 (in our species) almost exclusively on rocks, in more or less 

 compact cushions. Leaves crowded, more or less appressed 

 and somewhat contorted when dry, but not crispate, spreading 

 to squarrose when moist, lanceolate in general outline, margins 

 usually recurved and entire, except at the apex, which is often 

 hyaline, but is composed of the upper lamina instead of the 

 costa alone, giving the plants a hoary appearance in many spe- 

 cies; costa well developed; leaf cells short and rounded above, 

 almost opaque in most species, sometimes papillose; the lower 

 cells elongated, often rectangular and nearly hyaline. Calyptra 

 smooth; capsule ovoid to oblong, symmetric; immersed or 

 exserted; peristome single, of 16 teeth which are entire, per- 

 forate, or even cleft in some species. 



The genus is usually easily recognizable, but the species are 

 difficult and are often almost impossible to determine in sterile 

 specimens, as some of the critical leaf characters are variable. 

 The position of the margin (recurved or plane) seems to be a 

 fairly constant and useful character. Mature leaves from the 



