272 FRYE 
1 cell thick, wanting in Racelopus; marginal cells often of a different 
form from the others. Vein one, extending at least nearly to the tip. 
Inflorescence nearly always dioicous; sex organs terminal; antheridia 
in a rather large cup or disk through which the plant generally again 
grows. 
Calyptra narrow, often covered with a dense mat of branched 
hairs which are directed away from the point and end freely; if not 
with densely matted hairs, the apex of the calyptra is spinulose, or 
has few to many hairs, or is quite smooth. 
Capsule large, cylindric, or prismatic with 2—6 angles. Peri- 
stome present (except in Lyellia, Bartramiopsis and some species of 
Psilopilum), single; teeth 32 or 64, rarely 16, unbarred, ligulate, tri- 
angular in cross section. Columella expanded at the apex into a 
shield-shaped membrane (epiphragm) covering the mouth of the cap- 
sule and uniting with the tips of the teeth. Lid present. Pedicel 
long, smooth (except in Racelopus). Spores .co8 —.o21 mm., rarely 
larger, smooth or nearly so. 
Total number of genera, 10; number represented in western North 
America, 7. Total number species, about 320; number in western 
North America, 27. 
SYNOPSIS AND COMPARISON OF THE WORLD’S GENERA OF POLYTRI- 
CHACE. 
1. Calyptra with few or no hairs. 
2. Lamelle on upper side 18 or fewer. 
3. Lamina of 1 layer of cells. 
4. Leaves bordered. 
5. Peristome present. 
6. Stomates wanting on capsules. 
7 eke AISULCHECLELO tee ea err aan ae a Catharinea. 
4. Leaves not bordered. 
5. Peristome present; calyptra with few hairs; lamelle on 
vein at back of leaves in nearly all cases. 
6. Stomates present on capsule. 
7.0 Capsule teneve 2 ia% cham Lo: eee eee ee Oligotrichum., 
5. Peristome wanting; or if present, calyptra without hairs; 
without lamellze on back of leaves. 
6. Stomates present on capsule. 
7. Capsule somewhat flattened, elliptical in cross section. 
Psilopilum. 
3. Lamina composed of 2 layers of cells. 
4. Leaves not bordered. 
