THE POLYTRICHACEZ OF WESTERN NORTH AMERICA 3090 
4. Arista hyaline, rough, 13 mm. or shorter. 
5. Marginal cells of lamella ovate or flask-shaped, thickened, 
width to height about as 1:14-2. 
6. Capsule about as 1:1-14, sharply 4-angled. 
72) Plants 2-1 20cm. miei 
€.)) Stems mosthabranched. 4) 3.- 11. P. hyperboreum. 
4. Arista hyaline, rough, 3 mm. or shorter. 
5. Marginal cells of lamellz ovate or flask-shaped, thickened, 
width to height about as 1:14-2. 
6. Capsule about as 1:14-14, sharply 4~-angled. 
7. Plants 2.5—4 cnx high. 
Ca Seems SMA le en. a ee ceed ate 12. P. piliferum. 
1. Polytrichum gracile Dicks., in MSS. 
Name derived from gracilis = slender; probably referring to the 
rather tall stem, naked below. 
Plants tufted, dark green 2.5-10 cm. high. Stems matted to- 
gether below with whitish tomentum, simple or slightly divided, 
leafless below. 
Leaves erecto-patent, somewhat flexuous or patent when diy, 8-10 
mm. long, the limb lanceolate, gradually narrowed to a short acumen, 
limb usually about 4-6 cells wide in the middle of the leaf. Margin 
erect, sharply serrate, variable in width. Lamelle about 4o, 4-6 
cells high; marginal cells about equalling the others, not papillose, 
rounded or a little higher than wide; vein toothed above at back, 
excurrent; point short, red, dentate. Cells of limb .o15—.018 mm., 
round-quadrate to transversely elliptical; cells of sheathing base 
thin, rectangular, in middle of wing length to width about as 1 : 3-4. 
Perichetial leaves long-sheathing. 
Calyptra hardly covering the capsule. 
Capsule short, broadly ovate, inflated, erect, horizontal when 
dry, with s5—6 obtuse and often obscure angles, smooth, narrowed 
at mouth; hypophysis rather indistinct, hardly constricted above. 
Teeth often confluent and unequal. Lid large with a rather long 
beak. Spores .o18-.022 mm. Pedicel 4-5 cm. long, thin, flexuous. 
—On soil.—Kotzebue Sound north of Bering Strait, and Kodiak 
Island, Alaska; below White Horse Rapids, Yukon region, western 
British America; Rocky Mountain region of British Columbia; 
Eastern United States and British America. 
