136 American Midland Naturalist Monograph No. 6 



and mostly complete as in Bryum; spores mostly large; operculum convex to 

 obliquely rostrate; calyptra cucullate, narrow, mostly fugacious, smooth. 



Distributed over the whole earth, most abundant in damp woods and 

 swamps, on earth, bark of trees, or rocks, in the temperate zones. Five genera, 

 of which but one occurs in our region. 



1. Mnium Linnaeus, Hedwig 



Synoicous or dioicous, rarely autoicous: mostly robust, cespitose in bright 

 green to dark green or later brownish tufts; stem erect, often stoloniferous, 

 often bearing creeping flagelliform branches; leaves bract-like and remote below, 

 increasing upwards to the terminal rosette, broadly ovate, obovate, or oblong, 

 to spatulate from a narrow decurrent base, when dry contorted to crispate, when 

 wet erect-spreading to recurved, mostly with a border of 1-3 layers of elongate 

 prosenchymatous colored cells, each layer of the border usually sharply serrate; 

 costa stout; cells rounded to hexagonal, often collenchymatous and punctate, 

 uniform or smaller towards the margin: seta single or clustered, long; capsule 

 cernuous to pendent, rarelv erect, mostly oblong-ovoid, rarely arcuate; exothe- 

 cial cells rounded, annulus revoluble; teeth 16, strong, separate at base, green- 

 ish-yellow to reddish-brown, more or less papillose, the zigzag divisural line 

 distinct, the dorsal plates low, the trabeculae numerous, often united by spor- 

 adic cross-walls; inner peristome mostly yellowish-red, the basal membrane 

 half-v/ay to the apex and sometimes perforate; segments usually as long as the 

 teeth, lanceolate, mostly abruptly subulate, usually fenestrate and finally gap- 

 ing; cilia usually in 3's com.plete, mostly articulate; operculum convex to conic 

 and rostrate; calyptra narrowly cucullate. 



About 80 species, cosmopolitan, on various sub-strata, usually in moist or 

 shaded situations; about 30 species occurring in North America, about 11 

 species in our range. 



Key to the Species 



A. Leaves not cfistinctly bordered B 



A. Leaves distinctly bordered C 



B. Margin with a single series of low irregular teeth in the upper half; cells incras- 



sate 10. M. stellare 



B. Margin not distinctly toothed; cells thin-walled 12. M. cinclidioides 



C. Leaves with entire or almost entire margin D 



C. Leaves with serrate margin G 



D. Border indistinct and of one series of cells only 12. M. cinclidioides 



D. Border of 1-4 series of cells in 1-4 layers E 



E. Lid acutely rostrate; leaves obovate F 



E. Lid conic-apiculate; oblong to oval or sub-orbicular 9b. M. affine var. rugicum 



F. On stones; leaves usually minutely apiculate and percurrently costate 



1 1. M. punctatnm 



F. In swamps; leaves not usually apiculate and costa not usually reaching apex; 



often very large 11. M. piinct. var. elatum 



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 O 



H. Leaves serrate to the base or very nearly so I 



I. Teeth slender and usually of 2-4 cells 9a. M. affine var. ciliare 



I. Teeth usually of but one cell and not so slender J 



