402 BOTANICAL GAZETTE [DECEMBER 
level of the epidermis. The neck is not provided with a cover cell. 
It opens by the dissolution of the inner walls of the four terminal 
cells which border each other at a common line. As soon as fertiliza- 
tion takes place further development of archegonia normally ceases. 
Consequently two embryos on the same prothallium are rarely 
found, and since fertilization occurs after the opening of the canal, 
the embryo therefore lies very near the meristematic region. The 
growth of the embryo causes activity there to stop, and as a result 
it is found as a rule at the end of the prothallium. 
Antheridia appear earlier and more abundantly than archegonia, 
and are scattered throughout the entire upper surface of the pro- 
thallium. They are circular or oval in outline, and may be sub- 
merged entirely or may form a slight elevation on the upper part 
of the prothallium. They are isolated and never form antheridial 
masses similar to those very characteristic of L. obscurum to be 
described later. Figs. 58 and 59 show the latter stages in the 
development of the sperm. 
The sex organ primordia lie so close together that it is impossible 
always to say what kind of organ will develop. They may be 
separated by a single layer of cells, or, as Miss Lyon (3) observed 
in L. annotinum, they may touch one another. They are evidently 
of such a primitive nature that it is impossible to distinguish an 
antheridium from an archegonium in the very earliest stages of 
their development. There are some indications that the arche- 
gonial initial is slightly larger and longer than the antheridial initial, 
but this is so uncertain that it is useless as a criterion. 
As a result of this primitive condition, mixed sex organs are 
very frequently found. These may be normally shaped antheridia 
in which a few cells have never divided into sperm mother cells, 
or they may be archegonial in form, the neck filled with normal 
spermatogenous tissue, and the ventral canal and egg cells of 
female appearance (fig. 60). The opposite condition may also 
occur (fig, 61). Figs. 60 and 61 are sketches of two archegonia 
constructed from camera drawings of nine sections in serial order. 
Six abnormal organs of a bisexual nature were found on one pro- 
thallium. They of course always occur near the apex of the pro- 
thallium. The fact that sexual organs of a bisexual nature occur 
