VITTARIA LINEATA 205 
peripheral cells. It ruptures by the swelling of the peripheral 
cell or cells, and the portion of the pedicel immediately under the 
antheridium ; this drives the wall that separates them up into the 
antheridial cavity, and ejects the antherozoids. 
The archegonia occur among the rhizoids near the margin, on 
the under side of the older portions of the prothallium ; also on 
specialized branches which are formed at the margin of the main 
prothallium. They have slightly curved necks, but the rows of 
cells in both the anterior and posterior sides are equal in number. 
The rhizoids are unicellular, simple or branched, structures 
and are produced either directly from a cell of the prothallium or 
by the formation of an initial cell. 
The sporophyte consists of a creeping, dorsiventral rhizome, 
bearing its leaves ordinarily in two ranks. It frequently branches 
and the internodes of both stem and branch are so short that the 
leaves appear crowded together. The growing point appears as 
a fleshy green bulb which is densely covered by brown scales 
having a structure peculiar to this genus. The rhizome has a 
wedge-shaped apical cell and a concentric, tubular bundle, with 
foliar-gaps associated with the leaf- bundles. 
The roots are produced near the growing tip and are usually 
twice as numerous as the leaves. They have a normal root-cap 
and an axial diarch bundle, the two groups of xylem are gener- 
ally united after a time by large tracheids. The walls of the 
parenchymatous cells are strongly striated and in the young roots 
there are crystalline substances formed against the inner walls of 
the cells immediately under the epidermis. The roots branch fre- 
quently and the branching appears to bear a definite relation to 
the original xylem groups of the diarch bundle. 
There are three kinds of /eaves; first, the rudimentary ones 
which are spathulate and long-petioled, usually with a single 
central vein; second, the young sterile leaves, which are short- 
petioled, oblanceolate to linear, and show all gradations of vena- 
tion, from the simple central vein to the three veins which 
characterize the sporophyll. The sporophylls are short-petioled 
and linear. 
The venation of the leaf arises from two primary bundles, each 
giving rise to one smaller one which become the lateral bundles 
