MOSSES, LIVERWORTS, AND FERNS 271 
256. The rootstock of a fern. If the soil is carefully removed 
from the underground part of one of the common ferns, the 
horizontal rootstock (rhizome) appears (fig. 208). The lower 
side of the rhizome gives rise to the roots, and the upper side 
bears the leaves. At the tip of the rootstock is the bud, by 
means of which growth is continued from year to year. The 
leaf scars, or the bases of old leaves, 
may usually be seen upon the root- 
stock. The terminal bud grows 
forward each year from a fraction 
of an inch in some ferns to several 
inches in others, and at the begin- 
ning of each season it sends up 
one or more new leaves. 
The rhizome of the fern (fig. 209) 
presents the first really complex 
stem structure that we find as we st 
study the groups of plants in the 
order of their increasing complex- 
ity. This is a woody stem com- 
posed of several kinds of stem rhs 
tissues. Some of these tissues are = 
heavy-walled and give rigidity to 
the stem. The rhizome is some- 
times stored full of food in the gy. sootstock (rh) is horizontal 
form of starch. Some of the tissues and grows underground; upon it 
consist chiefly of rounded, fiber- °° een upHgnt 
like bundles which extend length- 
wise throughout the stem. These are the fibrovascular bundles, 
which term simply means “ fibrous bundles of vessels.” 
257. The leaf of a fern. As a fern leaf develops from the 
bud, it unfolds in a very peculiar fashion (fig. 211) known 
as cireinate vernation. The coiled or rolled (circinate) tip of 
the leaf is easily seen even in most old fern leaves. Mature 
fern leaves assume so great a variety of forms that it is impos- 
sible to give any description that holds good for many kinds, 
Fre. 208. The bracken fern 
(Pteris aquilina) 
