1897 | NORTH AMERICAN SPECIES OF AMBLYSTEGIUM 279 
ing from 4.5 to 8.5 in width and from 24 to 39 in length, in the 
middle costal region cells much shorter and oval-hexagonal, 7.5 « 
wide by 18 # long, midway between border and costa the cells 
still shorter, at the apex the marginal cells oval or subrhom- 
boidal, 9 # wide by 17 long, varying from 8 to 10m wide and 
from 14 to 20m long; perichetial leaves ovate lanceolate to 
lanceolate, the outer gradually acuminate, all erect, strongly 
costate, costa long excurrent. 
Sporophyte medium, 1 to 3°™ long: seta stout, 250 to 300m in 
diameter, dark purple below, yellow above ; central strand well 
developed, 30 to 38m in diameter, of thirty to forty rows of 
cells, walls of cells strongly thickened for this tissue ; cortex of 
three to four layers of cells, 4 to 13, passing gradually into 
ground tissue ; cells of this tissue ranging from 13 to 23 @: cap- 
sule oblong, unsymmetric, cernuous, with short collum, becom- 
img dark brick red with age, not constricted under the mouth 
when dry or only moderately so; cells of exothecium parenchy- 
matous on concave side, 23 wide by 32m long, ranging in 
Width from 20 to 26, and in length from 17 to 47, prosen- 
chymatous on convex side, 20 wide by 40m long, varying 
from 13 to 23 wide and from 30 to 65» long; cell walls 2 to 
3 thick ; three to five rows of isodiametric, quadrate or hexag- 
Onal cells under the mouth, 15 to 22m in diameter, walls 44 
thick ; stomata ten to twenty-five to the capsule, 30.5 ¢ wide by 
34.5 long, scattered ; peristome teeth lanceolate, golden yellow 
with a broad paler margin, serrate in the upper half, transversely 
striate on the back to near the middle, above this point dotted with 
Scattered papilla among the striae, the latter soon being replaced 
above by densely crowded ciliate papille ; endostome pale yel- 
low, equaling the teeth ; membrane two-thirds the length of the 
segments, the latter lanceolate, carinate, split, but not widely’ 
open along the keel between the articulations, finely papillose, 
cilia one to three, stout, shorter than the segments, nodulose ; 
©perculum apiculate from a convex or conic base ; annulus 
broad, of two to three rows of cells: calyptra equaling capsule, 
Split one-third its length. 
