158 BOTANICAL GAZETTE [SEPTEMBER 
between ooplasm and periplasm which is maintained until 
maturity, while before zonation such a differentiation did not 
exist. The process of differentiation is gradual, and a seriesol 
developmental stages has been obtained which seems complete. 
This period is the only one where the ooplasm possesses very 
few nuclei or none, and it is impossible to regard it as beinga 
period later than stages which present zonation and also contail 
50-100 nuclei (figs. 68, 69, 70). The development of the 
antheridial tube is such as to lend strongest support to tht 
sequence above indicated, since the tube is shorter in stages p= 
ceding zonation and longer in stages following it (see plates), 
thus affording strong corroborative evidence. While the differ | 
entiating line is characteristic of zonation the paucity of nucle 
in the ooplasm is equally so. The sharper the differentiatio® 
the fewer the nuclei, and when zonation was very definite ese 
could be found, and it is probable that when this stage is at its 
highest development there are no nuclei in the ooplasm. There 
is some evidence, however, that makes it seem possible that o7¢ 
and even two spindles sometimes remain in the ooplasm, but ths 
is uncertain. a 
No mention has been made, as yet, of the division of the nucle 
of the oogonium. This mitosis closely accompanies the proces 
of zonationas is indicated in most of the figures. These two even 
apparently take place nearly simultaneously. The oe 
60, 6r. At the time of complete zonation t 
metaphase and lie close to the line that separat 
from the periplasm (figs. 65, 66). Spindles are ae 
that actually cross this line at right angles, so that one bs, 
in the ooplasm and the other in the periplasm (78: A a 
The mitoses that take place at this period mark an see ? 
characteristic phase in the history of the 00g 0h an 
dividing nuclei that lie tangential to or wholly a : 
boundary line between the ooplasm and periplae | 
oe : es 
daughter nuclei in the periplasm. Each of t his the oosph® : 
ntly! 
cross the line (fig. 66) gives one daughter nucleus 
