288 FRYE 
PSILOPILUM Brid. 
Name derived from psilos = bare, and pilos = felt; referring to 
the absence of felted or matted hairs on the calyptra. 
Plants dioicous. Stems simple, from subterranean shoots. 
Leaves keeled or incurved, lanceolate or ligulate, not undulate, 
never toothed at back, 1 cell thick, when moist more or less patent 
from an indistinct sheath, when dry appressed or the tips incurved. 
Margin not bordered. Lamellaonupper side only, wavy from side 
to side, with crenulate edges; marginal cells similar to the others. 
Cells quadratic or round-hexagonal, rectangular at base. 
Calyptra cucullate, naked, or at tip papillose. 
Capsule usually inclined, more or less distinctly obliquely ovate, 
with small mouth, laterally compressed, smooth, with Jarge 2-celled 
stomates. Peristome present (in North American species); teeth 
usually unequal in size. Lid easily falling off, pointed to long and 
thinly rostrate from a conic base. Pedicels single. 
Number of species in western North America, 1; total number spe- 
cies, about 13. 
1. Psilopilum giabratum (Wahl.) Holz., in Bryologist, 5: p. 80 
(1902). 
Oligotrichum glabratum (Wahl.) Lindb., in Musc. Scand. p. 12 (1879). 
Psilopilum ischutschicum® (C. M.) Par., in Index,ed. 1,p. r1o4o. 
(1897). 
Psilopilum arcticum Brid., in Bryol. Univ. Vol. 2, p. 96 (1827). 
Name from glabrare = to deprive of hair; referring to the smooth 
calyptra. 
Stem 1—3 cm. high. 
Leaves very concave, muticous. Margin irregularly crenulate 
above. Lamella 7—10, disappearing toward the base. Vein van- 
ishing in the apex, smooth on the back. Cells small, long-rectangu- 
lar at the base. 
Calyptra very narrow, smooth. 
Capsule ferruginous, black when old, ovate-gibbous. ‘Teeth long, 
some of them 2-parted, thin. Lid short, convex-conic, with short 
incurved beak. Pedicel terminal, erect, brownish, .5—1.5 cm. long. 
8 Cardot & Theriot in Proc. Wash. Acad. Sci. 4, p. 327 (1902). 
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