1897 | NORTH AMERICAN SPECIES OF AMBLYSTEGIUM 281 
ingly branched, 5 to 20™ long, 250 to 400m in diameter, cylin- 
drical; central strand well differentiated though small, 20 to 27m 
in diameter, of ten to fifteen rows of cells; cortex of two to three 
layers of cells, usually not well differentiated, cells 8 to 22m in 
diameter, those of the ground tissue 17 to qo“; primary branches 
few, 2to 8™ long, prostrate, branchlets short, I to 3™, prostrate: 
leaves ovate lanceolate to linear lanceolate, long acuminate, 
terminating in a slender, straight, or curved point, 650 wide by 
2200p long, ranging in width from 450 to 7oom and in length 
from 1700 to 2400p, attaining greatest width in the basal fifth, 
many ranked, commonly complanate, occasionally equally 
spreading or subsecund, rarely erect, ordinarily more or less 
widely spreading, frequently folded or twisted when dry, costate, 
costa thin, extending through the lower half to three-fourths of 
the leaf, one-sixth to one-fifth its base at the line of insertion, 
50 to 75m wide, margin ordinarily very entire, rarely subserrulate ; 
leaf cells parenchymatous across the base, soon becoming 
prosenchymatous above, the basal cells quadrate to oblong, the 
One or two marginal rows narrower and longer, 16m wide by 
36.6 long, ranging from-13 to 20m in width and from 20 to 50 
in length; cell walls strongly thickened and sparsely pitted, in all 
parts of the leaf above the basal eighth the cells long hexagonal 
to linear, in the middle region 8.5 wide by gs» long, varying 
in width from 7.8 to gu and in length from 85 to 100#, fre- 
quently vermicular, cells of apical region shorter, 9.34 wide by 
34” long, ranging from 8.8 to 10m in width and from 28 to 384 
in length; outer perichetial leaves triangular-ovate, spreading 
from the middle, inner oblong, erect, all abruptly short acumin- 
ate and costate to the base of the acumen or nearly so, coarsely 
and irregularly serrate above or entire. 
Sporophyte medium, 1 to 3™ long: seta purple at base, light 
brown or yellow above, or uniformly pale brown throughout, 
170 to 260m in diameter, cortex of two to three layers of cells, 
6.5 to 15 in diameter ; central strand well differentiated, 30 to 
36.5 in diameter, composed of thirty to forty-five rows of cells; 
cells of ground tissue 9 to 26m in diameter: capsule short, oval, 
