1898 ] THE LEAF AND SPOROCARP OF PILULARIA 3 
The primary division of the semicircular segments or “ pri- 
mary marginal cells” is quite regular and at first resembles 
exactly that described by Poirault (’90) and myself for Marsilia. 
The first wall formed is a longitudinal and radial anticline (J, 
jigs. 3, 4) cutting off about one-third of the segment toward the 
dorsal side to form what we may call a section. The second is 
a similar wall (Z/, figs. 2-4) forming a second section next to the 
median wall of the leaf (or inner border of the segment), and 
leaving a ‘tertiary marginal cell” (m 03, fig. g). Then a trans- 
verse anticline (¢a’, figs. 2, 3) divides this marginal cell into two, 
an upper and a lower one. In each of these tertiary marginal 
cells a third longitudinal anticline appears (J//, figs. 3, 5) nearly 
parallel to wall I. At this point the similarity to Marsilia 
ceases, for instead of forming two more sections, as in that plant, 
each marginal cell of the fourth grade is here divided by a peri- 
cline (d w, fig. 6), thus ending its function as a marginal cell. 
The four primary divisions formed in each segment (leaving 
out of account the transverse anticlines which do not appear in 
a cross section of the leaf) develop in a way very like that 
found in the six primary divisions in the segments of the leaf of 
Marsilia. Section I very early cuts off by a pericline near the 
inner end (f/ w, fig. ¢) a cell which is to function as procam- 
bium. The outer end of the section is soon cut in halves by a lon- 
gitudinal anticline (4a, fig. 4). Thensections II and III and the 
marginal cell form procambium at their inner ends (p/w, fig. 6), 
while at the outer ends of all the sections periclines, correspond- 
ing to that in the marginal cell, separate the protoderm and 
ground meristem layers which encircle the procambium (figs. 6, 
7). No second portion of procambium is ever formed in section 
I, as happens in Marsilia. 
The protoderm layer soon divides by periclines into epidermis 
and hypodermis (epand xk y, figs. 7-9) and the cells of these 
then divide by anticlines to form many cells, but each layer 
remains of a single cell in thickness even at maturity, as no more 
periclines are ever formed. The procambium throughout breaks 
up by numerous longitudinal walls and fewer transverse ones to 
