OF WESTERN PENNSYLVANIA 109 



4. Slender small plants in dense cusliions; central strand in 



stem; teeth decidedly cribrose. 2. G. conferta. 



d. More robust, loosely cespitose; no central strand; teeth slight- 

 ly cribrose. I. G. apocarpa. 

 e. Leaf-cells without sinuose walls; capsule oblong. 



(G. ambigua [SuUivant] 

 Sullivant.) 

 e. Leaf-cells with somewhat sinuose walls; capsule oblong-ovate. 



3. G. pennsylvanica. 

 i. Capsule distinctly ribbed; seta curved; leaf-margins of a single 



layer of cells. (G. olneyi Sullivant.) 



f. Capsule smooth, seta straight; upper leaf-margins of more than 

 one layer of cells. g. 



g. Leaves lanceolate, tapering; basal leaf-cells thin-walled and elon- 

 gate-rectangular, about 1 :4 to 1 :8, alpine. (G. obttisa Schwaeg- 



richen ; G. doniana 

 Smith.) 

 g. Leaves oblong-lanceolate, the long apex rough, piliferous; basal 

 leaf-cells more or less quadrate. 4. G. laevigata. 



1. Grimmia apocarpa [Linnaeus] Hedwig. 



(Plate XIV) 



Loosely cespitose, more or less erect, branching rather 

 freely, about 2 cm. high, dull olive-green, drying stiff and non- 

 crisped : leaves ovate-lanceolate, erecting-spreading, strongly 

 costate and usually more or less carinate, margin narrowly re- 

 curved, apex narrowly obtuse, leaves about 2 mm. long; 

 perichaetial leaves similar but somewhat longer and thinner ; 

 costa ending in or just below the apex, terete dorsally; basal 

 cells rectangular, about .0O8-.O10X-015-.O30 mm., upper 

 basal cells quadrate, and in our specimens usually sinuose- 

 walled, the median and upper cells rounded and .005-009 mm. 

 in diameter, all cells incrassate and more or less opaque : seta 

 erect, stout, about 0.5 mm. long; capsule immersed, oval- 

 oblong, about 1 mm. long, reddish-brown, rather thick-walled, 

 smooth ; calyptra short, lobed ; operculum low-conic, rostrate ; 

 peristome single, teeth 16, lance-linear, trabeculate, somewhat 

 cribrose, reddish-brown, faintly papillose, when dry refliexed- 

 revolute ; spores reddish-brown, in our specimens about .012- 

 .018 mm. in diameter; columella falling away with the opercu- 

 lum and remaining attached to it ; spores mature in late spring. 



On stones, hard earth, etc., with a wide distribution over 

 the colder regions of the earth. In America occurring from 

 Alaska and Newfoundland to the Northern States and south 

 in the mountains to Georgia. 



Fayette : Cheat Haven, September 3-6, 1910. O. 



E. J. and G. K. J. 



McKean : D. A. B. (Porter's Catalogue). 



Washington : Linn and Simonton. (Porter's Cata- 

 logue). 



