OF WESTERN PENNSYLVANIA 159 



costate. 10. M. punctatum. 



f. In swamps; leaves not usually apiculate and costa not usually 

 reaching apex; often very large. 10. M. pttnct. var. datum. 



g. Leaves serrate with a single row of teeth, h. 

 g. Leaves serrate with a double row of teeth. 



k. 

 h. Leaves serrate only in upper two-thirds. 



6. .17. cuspidatnm. 

 h. Leaves serrate to the base or very nearly so. 



i. 



i. Teeth slender and usually of 2-4 cells. 8. M. affinc var. ciliare. 



i. Teeth usually of but one cell and not so slender. 



j. Leaf apex bluntly rounded, abruptly apiculate. 



5. M. rostratum. 

 \. Leaf apex more or less acute and cuspidate. 



7. M. medium. 

 k. Leaves lanceolate; costa incomplete, dorsally toothed. 



1. M. h or num. 



k. Leaves wider than lanceolate; costa usually complete in upper 



leaves at least. 1. 



1. Co.-ta toothed dorsally. in. 



1. Costa not toothed dorsally. n. 



m. Cells not collenchymatous. about .014-.018 mm. 



2. M. orthorrhynchwn. 

 m. Cells collenchymatous. about .020-.030 mm. in diameter. 



.17. lycopodioides.* 

 n. Cells rounded and strongly collenchymatous. 



3. M. scrratum. 

 n. Cells angled and not collenchymatous. 4. M. spinulosum. 



1. Mnium hornum Linnaeus, Hedwig. 



(Astrophyllum hornnin Lindberg). 



A robust species in dense tufts, with erect unbranched 

 stems and terminal rosettes of leaves which reach a length of 

 3-5 mm. but are oblong- to narrowly elliptic-lanceolate, acute, 

 sharply apiculate, all leaves with a reddish, thickened border, 

 sharply doubly spinosely serrate in the upper half; the costa 

 ending below the apex and spinose dorsally above ; leaf-cells 

 incrassate, angular, not very regularly seriate, rather small: 

 seta solitary, long; capsule subpendulous, finally horizontal, 

 ovate-elliptic and tapering to a distinct neck, when old pale 

 yellowish with a red mouth ; operculnm conic-apiculate : 

 dioicous. the antheridial flowers being disc-like. The leaves 

 are proportionally narrower than the other species of the 

 genus and the calyptra often remains for a time clasping the 

 seta just below the capsule, mature in April to May. 



In shaded, swampy or springy places and banks of streams : 

 Europe, Algeria, Japan, North America from Newfoundland 



*Mnium lycopodioides (Hooker) Schwaegrichen, as reported from 

 Blair and Elk Counties in our region (Porter's Catalogue), is probably 

 synonymous with Mnium pseudo-lycopodioides C. Mueller and Kindberg, 

 which appears to be hardy separable from Mnium orthorrhynchum (Bridel) 

 Bryologia Europsea. 



