1897 } NORTH AMERICAN SPECIES OF AMBLYSTEGIUM 287 
one or three, nodose to imperfectly appendiculate, usually 
shorter than the segments, occasionally equaling them ; opercu- 
lum as wide as the capsule, blunt pointed from a convex base : 
spores finely papillose, 16 to 23m in diameter: calyptra equal- 
ing the capsule or nearly so, split half its length. 
Has.: In moist shady places on earth. Type locality Ger- 
many. 
Europe, Asia, North America: District of Columbia, Min- 
nesota(?), Kansas. Not common. 
Closely related to 4. rifarium, the smaller forms of which it resembles. 
It may generally be known from these by the long slender acumen and ser- 
rate margin of its leaves. It may be confused with large forms of A. varium. 
The leaves of the latter are commonly shorter pointed and have the leaf cells 
smaller throughout and especially shorter at the base. 
AMBLYSTEGIUM VACILLANS (Sulliv.). Plate XVI. fig. 4. 
SYNON.: Amblystegium vacillans Sullivant, Mss. 1870. Icon. Muse. 
Suppl. 96. 42. 72. 1874. Macoun & Kindberg, Cat. Can. Pl. 6:222. 1892. 
Hypnum vacillans Lesquereux & James, Man. Moss. N. Amer. 377. 1884. 
Gametophyte bisexual, medium to large, loosely cespitose, pale 
yellowish green: stems prostrate or floating, sparingly branched, 
2 to 6™ long, 175 to 385 in diameter; central strand poorly 
differentiated, 20 to 30m in diameter, composed of six to ten rows 
of large cells, 6.5 to 12min diameter; cortex of three to five 
layers of cells 6 to 17, those of the ground tissue abruptly larger, 
17 to 35m; branches short, 1 to 2™ long: leaves lanceolate to 
oblong lanceolate, attaining greatest width in basal third, acumi- 
nate or acute, tip broad and blunt, slender, entire, costate, costa 
distinct, extending three-fourths to four-fifths the length of the 
leaf, about one-seventh the leaf base at line of insertion, 35 to 
47 wide; many ranked, complanate or equally spreading 
On the branches, open erect, in small plants 4oou wide by 13404 
long, ranging from 330 to 450m wide and from 1050 to 1550 
long, in larger plants reaching 6854 wide by 2150m long; leaf 
Cells parenchymatous at base, leaf ordinarily separating from the 
Stem leaving at the basal angle a small group of quadrate or 
