2 55 
of Pilularia globulifera , Z. 
divisions, but only in two planes, there never being any 
horizontal walls formed, so that the segments of the root-cap 
form single layers of cells, and its stratified structure as seen 
in longitudinal section is very marked. 
The Stem-quadrant. 
The stem quadrant, like that of the leaf, divides first 
by a regular octant-wall, and the resulting octants grow for 
a time in the same way. As in the root, the apical cells 
are distinguishable from the first, each octant in fact func- 
tioning as such from the beginning, and dividing by segments 
cut off in regular order from the three inner faces of the 
octant, which has the tetrahedral form that characterizes the 
apical cell of the older stem. The first wall in each octant 
(PI. XIV, Fig. ii y) meets octant- and quadrant-walls, and cuts 
off a large cell which is in contact with the foot, and according 
to Hanstein and Arcangeli is to be regarded as part of the 
foot. That physiologically this is the case is indisputable, as 
these cells, lying as they do next the basal cells of the pro- 
thallium, must help to absorb the nutriment from the spore. 
As, however, these segments are cut off from the stem-quad- 
rant, and not from the foot itself, and are in all essential par- 
ticulars both in regard to form and methods of division like 
the later segments, it seems more in accordance with the facts 
to regard these segments, morphologically at least, as the first 
segments of the stem and second leaf, and the equivalent of 
the later ones. 
Hanstein’s statement that the first wall in the stem-quad- 
rant of Marsilia corresponds to the wall in the accompanying 
figures, and that the octant-wall is formed subsequently, is not 
confirmed by later observers, nor was it found to occur in any 
instance observed by me in Pilularia , 
Of the two octants, one becomes the stem and the other the 
second leaf, corresponding with the earlier observations of 
Hanstein and Arcangeli. These are often not to be dis- 
tinguished from each other for some time, but as a rule the 
