THE POLYTRICHACEZ OF WESTERN NORTH AMERICA 287 
1. Cell walls in upper half of leaf approaching leaf margin diagonally. 
2. Cells about midway between base and tip .o20-.030 mm. in their 
longer diameter. 
3. Leaves entire or nearly so. 
4. Vein smooth at back. 
5. Capsule distinctly plicate. 
pares wa 
DOR Basse 
aay 
~ 3 
wee os oe ee a we ee — ww ee wo ow oe we ow em meee - 2 ere eames cece mewn 6 oe oem ero 2 ee re oe etme mw mene ewe ernment 

Fig. 8. Comparison of Oligotrichum incurvum (upper figure) with Oligotrichum 
incurvum var. latifolium (lower figure). 
1 and la = Leaves, upper side, one narrower than the other. In 1 the margin is 
usually serrate where it is rolled in, X 15. 2 and 2a = Leaf-tips, one usually with 
serrate lamellz on the back, the other not, X 65. 3 and 3a = Portions of leaves show- 
ing difference in size of leaf cells; also the cell walls meeting the margin perpendicu- 
larly in 3 and diagonally in 3a, X 500. 
On Soil—St. Lawrence Island, Bering Sea.’ 
7 Kindberg reports this from Rogers Pass, Selkirk Mountains, B. C., but an examina™ 
tion of this material shows that in areolation, direction of marginal cell walls, and size 
of leaves it is nearer to the type than to the variety. The leaf margin of O. incurvum 
sometimes approaches entirety, and the back smoothness. O. incurvum var. lati- 
folium is therefore known only from St. Lawrence Island. 
Proc. Wash. Acad. Sci., August, 1910. 
