OF WESTERN PENNSYLVANIA 67 



inserted belo\\ the edge of the capsule; teeth mostly 2-3- 

 parted to the middle, vertically striate below, ventrally 

 trabeculate ; calyptra not ciliate at base. 



A cosmopolitan genus of about 150 species, mostly on non- 

 calcareous sub-strata, in the tropics confined to the mountains 

 and rather rare in the Southern Hemisphere. In North 

 America about 65 species are known and at least 7 species 

 occur in our region. 



Key to the Species. 



a. Capsule cernuous, unsymmetric. b. 



a. Capsule erect, symmetric. g. 



b. Leaf-cells porose. c. 



b. Leaf-cells very slightly or not at all poro>e. 



(D. subnlctoniin R. and 



C.) 

 c. Leaves transversely undulate; costa not reaching apex. 



d. 

 c. Leaves not transversely undulate; costa percurrent to excurrent. 



f. 



d. Upper leaf-cells elongated. 1. D. polysehtni. 



d. Upper leaf-cells iso-diametric. e. 



e. Capsule solitary; costa and lamina dorsally smooth. 



(D. bcrgeri Bland.) 

 e. Capsules clustered: costa and lamina dorsally rough. 



(D. drummondii C. M.) 

 f. Capsules clustered: guides of costa in two rows. 



(D. ma jus Smith.) 

 f. Capsules solitary: guides of costa in one row. 



2. D. scopariuin. 

 g. Costa with median guides. h. 



g. Costa without median guides. 2 4-stratose. 7. D. longifoHum. 

 h. Entire lamina uni-stratose; costa percurrent. 



i. 

 h. L'pper lamina more or less bi-stratose: costa excurrent. 



j- 

 i. Upper leaf-cells rectangular and mamillate dorsally. 



3. D. montauinn. 

 i. L'pper leaf-cells less regular, not mamillate. 



4. D. flagellare. 

 j. Costa and margin entire, apex usually broken off. 



6. D. viridc. 

 j. Costa and margin serrulate. 5. D. fnh'uin. 



1. Dicranum polysetum Swartz, Schwaegricben. 



(D. mgosnui Rriclel ; D. undulatnin Khrhart). 



Tall, up to 20 cm. or more, loosely cespitose : stems erect 

 or decumbent, densely radiculose below; leaves undulate, 

 lustrous yellowish-green ; 6-9 mm. long, lanceolate, the upper 

 half spinosely serrate, the lower half with recurved margin ; 

 costa strong, rather narrow, vanishing in the apex, with two 

 serrate dorsal lamelke above; alar cells distinct, brownish, not 

 reaching costa. median and upper leaf-cells elongate-elliptic to 

 linear-fusiform, incrassate and porose: seta long, reddish, 



