1912] CHAMBERLAIN—CERATOZAMIA 5 
genus. The sporangia are crowded over the entire abaxial surface 
of the sporophyll, with only a 
slight indication of any division 
into two groups by a sterile line 
through the center (fig. 3). The 
sori consist of three or four spor- 
angia, with some two’s and occa- 
sionally a single sporangium, the 
single sporangium being found 
more frequently at the top and 
bottom of the strobilus. The 
soral character is not always evi- 
dent in a surface view, but is 
rather distinct after the pollen 
has been shed (fig. 3, c), and is 
easily seen by removing the spor- 
angia or by examining sections 
(figs. 3,4). Dehiscence begins in 
the peripheral sporangia of the 
sporophyll and progresses toward 
the axis of the cone, as shown in 
fig. 3,0. Asin Dioon edule, the 
wall of the sporangium is thin 
at the sides and thicker at the 
top, with a thick-walled outer 
layer of cells and thin-walled cells 
between this and the sporogenous 
tissue. The dehiscence is marked 
by two rows of thin-walled cells 
which contrast sharply with the 
thick-walled cells of the rest of 
the outer layer. The cells of the 
outer layer are elongated parallel 
to the dehiscence, so that in a 
section at a right angle to the 
dehiscence they are almost square 
in outline (fig. 5), while in a sec- 
Bs 
a 
Fic. 2.—Staminate strobilus; 3. 
