496 BOTANICAL GAZETTE [JUNE 
that it pulls both the filaments and the vertical walls of the air 
chambers diagonally backward, giving the chamber a more or less 
distorted appearance (figs. 4-7). 
A really surprising amount of differentiation is seen in the cells 
of the solid portion of the thallus. The commonest and most usual 
is a strand of stumpy cells, filled 
with oil globules and food gran- 
ules, which passes longitudinally 
through the center of the thallus, 
and ends around the foot of the 
sporophyte. Besides this, there is 
frequently a strand composed of 
the ordinary elongated cells, with 
their walls thickened by an 
Fic. 9.—One member of the ring of irregularly wound tangle of fibers, 
collapsed cells which surround the air ‘ . 
also running the entire length of 
the thallus. 
Vegetative reproduction.—The dichotomous branching, which is 
so common in the other members of the Marchantiales, is here 
almost entirely replaced by the oc- 
currence of branches arising from the 
ventral surface. These branches have, 
for the most part, at maturity a stalk- 
like base, through the dying away of 
which the branches are set free as inde- 
pendent plants, and will then them- 
selves multiply in the same fashion. 
In their origin, these adventitious 
branches have absolutely nothing to —— F%6- 10.—Appendage to ven- 
do with the apical cell. This was solo igs tei a 
clearly seen in several of the prepara- — 
tions studied, where, on a plant bearing two young branches, the 
older one was placed between the apical cell and the younger. 
Archegonia.—The archegonia are borne terminal on the thallus. 
They follow so closely the general line of individual development for 
the Marchantiales, that it is not necessary to repeat it here. They 
arise in two rows in acropetal succession. The surface, or pad, on 
