CC 64} al yl ae 
Tene 
1897 | NORTH AMERICAN SPECIES OF AMBLYSTEGIUM 245 
Il. Leaves plainly costate. 
A. Leaves with a distinct border. 
Costa joining border at apex : : - : f : . A. lescurit. 
B. Leaves not bordered. 
* Costate to apex or nearly so. 
Leaves acuminate, basal cells abruptly enlarged , ‘ A, irriguum. 
Leaves acuminate, basal cells not enlarged. 
Serrate throughout ‘ Z P . A. compactum. 
Entire, or obscurely — shore. 
Acumen long, costa ceasing within it . . A. varium. 
Acumen short, costa very strong, usually long kxshansense 
A. noterophilum. 
Leaves not acuminate, ovate to oblong lanceolate, tip blunt A. fluviatile. 
* * Costa disappearing at the middle or above. 
[A. compactum may be sought here. ] 
Cells near the middle of the leaf 1: 10-15. 
Leaves long acuminate, apex sharp. .  . A, riparium. 
Leaves acute or short acuminate, apex — : : . A. vacillans. 
Cells near the middle of the leaf 1: 8 or less. 
Alar cells quadrate or transversely elongated . ‘ ‘ A, serpens. 
Alar cells oblong. 
Leaves 6.9-1.2%0.95-0.37™™ . ; ‘ ; A, juratzkanum. 
Leaves 1.2-1.6X0.5 —0.7™™ ‘ ‘ . ‘ . A. kochit. 
AMBLYSTEGIUM MINUTISSIMUM (S.& L.) Jaeg. & Sauerb. Plate X7. 
FE. 4: 
SYNON.: Aypnum minutissimum Sulliv. Musci and Hepat. of U. S.— 
(78) (issue of 1871). 1856.—Sulliv. & Lesq. Icon. ig 195. pl. 120. 
1864.—Lesq. & James Man. Mosses of N. Am. 371. 
Amblystegium minutissinum Jaeg. & Sauerb. phoeh 4 2: 547.—.—Mac- 
oun & Kindberg Cat. Can. Pl. 6: 216. 1892. 
Exsiccati: Aypnum confervoides Sulliv. Musci Allegh. 31 (in part). 
Hypnum minutissimum Sulliv. & Lesq. Musct Bor, Amer. (1st ed.) 343- 
(2d ed.) 520 (Herb. Wis.). 
TYPE in Herb. Sulliv., Cambridge, Mass. 
Gametophyte bisexual, very minute, pale green : stems prostrate, 
appressed, irregularly subpinnately branched, cylindrical, 60 to 
110 # in diameter; central strand none; cortical region of one 
to two layers of oaths, not well differentiated, walls thin, cells 
