258 BOTANICAL GAZETTE [ocToBER 
Exsiccatl: Aypnum serfens Sulliv.and Lesq., Musc. Bor. Amer. (1sted. 
345. (2d ed.) 523.— Macoun, Can. Musc, 318 (Herb. Wis.). 
Amblystegium serpens Austin, Musc. App. 373. 
Type probably not in existence. The plant is supposed to have been 
described as early as 1696 by Ray. 
Gametophyte bisexual, small or of medium size, usually densely 
cespitose, occasionally in loose mats, sometimes bright green, 
oftener dull yellowish green: stems prostrate, generally much 
branched, slender, weak, 100 to 150m in diameter, 1 to 3™ long; 
central strand well differentiated though small, 13 to 20% in 
diameter, composed of eight to fifteen rows of cells; cortex of 
one or two layers of cells with walls moderately thickened, cells 
6.5 to 13H; cells of ground tissue 13 to 30m in diameter, 
branches ascending or erect, flexuous with few branchlets .5 to 
1.5 long: leaves ovate lanceolate to narrowly lanceolate, 3204 
wide by 800p long, varying in width from 260 to 360, and in 
length from 500m to more than a millimeter, usually serrulate in 
upper two-thirds, flat or concave at base, generally long acuminate, 
occasionally subsecund, costate, costa thin, weak, reaching to near 
the middle, occasionally beyond (three-fifths the length of the 
leaf), or sometimes very short, occupying one sixth the leaf base 
at the line of insertion, 25 to 35 wide, maximum width of leaf 
in basal sixth, upper two fifths a long slender acumen, leaf grad- 
ually widening below, when moist erect or open-spreading, in the 
dry condition either open or appressed ; leaf cells parenchy- 
matous below, those of the alar regions short rectangular to 
slightly transversely elongated, 17.4 long by 15.3 wide, varyng 
from 13 to 18“ in width and from 15 to 1gp in length, in the 
costal region of base cells usually longer, the quadrate alar cells 
extending up to widest point of the leaf, there giving place to 
rectangular ones which in turn are soon succeeded by regularly 
hexagonal cells; those of middle lamina 11 wide by 424 long, 
ranging from g to 13 wide and from 30 to 55m long, the longest 
cells however usually being found in the long slender acumen, 
where they sometimes reach 60p, varying in width from 11 to 13F 
and in length from 40 to 60p, averaging 12m wide by 454 long > 
pericheetial leaves triangular lanceolate to oblong, erect, some- 
MEME icp 
