— 2 
thick, vanishing below the apex, its cells in cross section subequal. Cells of 
leaf-base near the vein somewhat rectangular or sublinear, not sinuose; cells 
of leaf-tip and leaf-middle round or short-ovate, 8-12^ wide, incrassate at the 
side, smooth but convex on both sides of the leaf, very strongly convex on the 
upper side. Perichaetial leaves much larger than the others, at base somewhat 
subvaginate, long-acuminate, erect when moist. Seta short, purple but finally 
blackish, twisted to the right when dry, about 5 mm. long. Capsule erect, 
narrowly cylindric, 1.5 mm. long, .3 mm. in diameter. Spores minutely granulose, 
16-ijn in diameter. Otherwise unknown. — Known only from Muir Glacier, 
Alaska. 
Type material was kindly lent by the Missouri Botanical Garden. It con- 
tained only 2 capsules, both mature, without teeth. There was no mature 
calyptra nor lid. Cardot & Theriot evidently also lacked these. There is some 
doubt whether it is a Rhacomitrium at all. The leaf-cells look more like those 
of Grimmia, but the capsule is rather long for that genus. The final disposition 
of the plant will likely have to await specimens with peristome. 
5. Rhacomitrium heterostichum (Hedw.) Brid. Mant. p. 79. 1819. 
Plants green to grayish-green. Stems up to 6 cm. long; elongated branches 
none to few per plant, short tuft-like lateral branches none to fairly common. 
Rhacomitrium, heterostichum. (1) Plant, Xi. (2) Cells of leaf-middle, X400. (3) Leaf, 
Xi7- (4) Leaf-tip, X200. (5) Capsule, Xi7- (6) Cross section of margin in upper part of leaf, 
X550. 
Plate II 
