Leaf and Sporocarp in Marsilia quadrifolia , L. 131 
The Capsule. 
In the seventeen or eighteen segments forming this part 
of the sporocarp, we find that plerome- and dermatogen- walls 
are formed in each section, as in those of the petiole (Figs. 27, 
28), and the halving anticline of section I is followed by 
periclines cutting off another portion of plerome from each 
half. The dorsal bundle, which is a continuation of the axial 
bundle of the stalk, is made up entirely from the plerome 
of section I (d.b., Fig. 31), some of the cells of which differ 
from all others of the capsule by remaining of the full length 
of the segment. The bundle is thus much more restricted 
in origin than that of the petiole. 
The dermatogen-layer in the capsule splits, as in the leaf, 
into epidermal and hypodermal layers, of which the former 
remains one cell in thickness and gives rise to stomata and 
deciduous trichomes, while the latter divides {hy.> Figs. 39,31) 
to form the two layers of thickened cells of the wall of the 
mature capsule, differing thus from the hypodermis of the leaf 
(Fig. 10). The periblem of the capsule gives rise to the 
several layers of loosely packed cells between the vascular 
bundle and the hypodermis, and between these cells and the 
latter are developed the numerous but small air-canals con- 
fined mostly to the dorsal side (a. c ., Fig. 29) and separated 
by partitions arising like those in the petiole. 
In the first three segments at the base of the capsule no 
sori are formed, but there is formed in the youngest pair from 
the plerome of sections III and IV, in a way to be described 
in treating the soral segments, a forked lateral branch of the 
dorsal bundle (Fig. 44). The plerome of sections II, V, 
and VI of this pair of segments, and all but section I of the 
next older pair, is apparently devoted to the formation of 
the basal portion of the gelatinous ring on which the sori are 
borne when the capsule bursts. In the oldest pairs of seg- 
ments there is formed a two-layered wall of thickened cells, 
like those of the hypodermis, stretching completely across the 
