170 
5. BRACHYTHECIUM ACUTUM (Mitt.) Sull. Icon. Musc. Suppl. 99: 
WF 1874. 
Hypnum acutum Mitt. Journ. Linn. Soc. 8: 33. pl. 6. 
Brachythecium mammilligerum Kindb. Macoun, Cat. Can. Pl. 6: 
192: 1792. 
Gametophyte in wide thin glossy-green to yellowish-green 
mats; stems prostrate, creeping or sometimes floating, 5-10 cm. 
long, irregularly divided, radiculose at base, branching irregularly 
pinnatifid; branches few, 5-10 mm. long, frequently somewhat 
complanate-foliate, not radiculose; branch leaves distant, open, 
lanceolate to ovate-lanceolate, gradually narrowed from just above 
the base, ending in a very slender point, 1.6—2 X 0.5-0.7 mm., 
distantly serrate or entire, very slightly concave, little or not at all 
plicate ; costa extending two-thirds the length of the leaf ; median 
cells linear-vermicular, 10: 1; basal and alar cells shorter and 
broader, oblong-rhomboidal to quadrate; stem leaves slender 
pointed, triangular-ovate, nearly entire, 2-2.5 by 1 mm. : monoi- 
cous, sometimes polygamous ; perigonial leaves ovate-acuminate, 
bordered by a row of elongated cells: perichaetium 2.5 mm. long ; 
the inner leaves ovate-lanceolate, sheathing at base, open above, 
abruptly long-filiform acuminate, ecostate. Sporophyte 2.5—3.5 
cm. high ; seta smooth, red-brown, often lighter colored above ; 
capsule red-brown, oblong-ovoid to short cylindric, 3 mm. long, 
3:1, arcuate and inclined, occasionally nearly symmetric ; oper- 
culum long conic, apiculate ; annulus simple, of 1 or 2 rows of 
cells ; teeth of peristome subulate-lanceolate, orange ; segments 
nearly as long as teeth; cilia 2 or 3, well developed, strongly 
nodose or appendiculate; spores minutely roughened, 13-15%, 
maturing in autumn. ; 
Type seen, from Pack River, British Columbia (Lyall) in 
Mitten herbarium. On the ground and rotting logs and in moist 
and swampy places. Northern United States and Canada, across 
the continent; south to N. J., Ohio and Colorado. Macoun, 
Can. Cryptogams 110 (B. salebrosum mammilligerum). . 
ILLUsTRATIONS.—Mitt. L c.; Sull Lc. 
Exsiccati.—Austin, Musc. Appal. 316. 
A careful comparison of a large number of specimens indicates 
