33° BOTANICAL GAZETTE [NOVEMBER 
portion of the leaf. This bordered appearance is often made 
more conspicuous by the involute character of the leaf margin. 
A border of this sort has long been emphasized as one of the 
most important characters separating O. Sphagni from O. denu- 
datum. The border of O. Sphagni (fig. go), however, is much 
less distinct than that of O. prostratum (figs. 57, 58). In both 
species we find two to four rows of marginal cells which exhibit 
a tendency, sometimes very clearly marked, to be arranged in 
radial rows as well. These marginal cells have uniformly 
thickened walls, giving them a very different appearance from 
the thin-walled median cells with their small trigones. In O. 
prostratum the leaves exhibit considerable variation, not only 
with respect to the width of the border, but also with respect to 
the thickness of the walls of the marginal cells, and the two 
extreme conditions represented in the figures are connected by a 
series of intermediate forms. Both in this species and in 0. 
Sphagni, the border is indistinct in poorly developed individuals. 
UNDERLEAVES. 
The underleaves of Odontoschisma present peculiarities which 
have been strangely overlooked by writers on the genus. In the 
specimens of O. Macounii from Greenland and Yukon, these 
underleaves are especially large and persistent even on sterile 
stems, although they are considerably smaller on Minnesota 
specimens of the same species. Their most remarkable feature 
is found in the slime-secreting papillae which are borne in large 
numbers on their margins. Similar papillae are found on the 
underleaves of our other species of Odontochisma, but they are 
usually shorter-lived than in O. Macounii. 
Leitgeb and others have already called attention to the fre- 
quent occurrence of papillae in connection with the growing- 
points of the Hepaticae. In the Jungermanniaceae they seem 
to be almost constantly present, but are usually restricted to the 
postical segments cut off from the apical cell. Leitgeb desig- 
nates these papillae as “primordial,” and looks upon them as 
structures which the leafy hepatics have inherited from their 
thallose ancestors.** When the postical segment is cut off in 
Unters. iiber Lebermoose 2:7 ff. 1875. 
