384 BOTANICAL GAZETTE [DECEMBER 
sectioned. But the mature stem, especially the region at which 
it branches, has proved to be of chief interest from the stand- 
point of questions of comparative anatomy. 
THE STEM. 
GENERAL ANATOMY.—The mature stems are very stout rhi- 
zomes, exceptionally so in 7. barbara, which grow in a direction 
somewhat oblique to the horizontal. The leaves are in a closely 
set tuft at the anterior end, for they are annual and the inter- 
nodes are very short. The broadly winged, overlapping bases 
with their sclerenchymatous sheaths resist decay long after the 
remaining portion of the leaf has perished, and these, together 
with the roots, which are very numerous, greatly add to the 
bulk of the stem. The stem usually bifurcates once into two 
branches of equal size, which lie in a horizontal plane. A few 
specimens of O. regalis were found, however, in which one of the 
forks was much larger than the other, but the larger almost 
immediately divided again, so that there were three branches of 
about the same size lying in the same plane. The forking bears 
no relation to the number of leaves produced, counting from the 
cotyledons, nor to the age of the plant. Occasionally there is 
no branching at all, though maturity has long since been 
attained, while in rare cases it has taken place comparatively 
early in the life of the fern. 
The rhizome exhibits a very characteristic appearance in 
cross-section (fig. r). The outer portion, the thick external 
cortex (ex. c.), consists of very resistant, dark-brown scleren- 
chyma, in O. ctnnamomea of a rich red-tinted brown, in O. regalts 
and the Todeas of a black, and in O. Claytoniana of a dull brown 
hue. The cortex is marked by leaf-traces (/¢), which form a 
close spiral, and at the nodes by the escaping roots (7). In 
_O. cinnamomea sclerification of the cortical tissue is later in 
taking place than in the other species. The internal cortex (7. ¢.) 
is parenchymatous, comparatively narrow, roughly pentagonal, 
and its cells are heavily loaded with starch grains, Passing 
the pericycle and the bast region, which form a complete 
