272 FRYE 



I 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, hgulate, 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 .008 — .021 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^. 



I. Calyptra with few or no hairs. 



2. Lamellae on upper side 18 or fewer. 

 3. Lamina of i layer of cells. 

 4. Leaves bordered. 

 5. Peristome present. 



6. Stomates wanting on capsules. 

 7. Capsule terete Catharinea. 



4. Leaves not bordered. 



5. Peristome present; calyptra with few hairs; lamellae on 

 vein at back of leaves in nearly all cases. 

 6. Stomates present on capsule. 



7. Capsule terete Oligotrichum. 



5. Peristome wanting; or if present, calyptra without hairs; 

 without lamellae 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. 



