80 BOTANICAL GAZETTE [AUGUST 
after the nuclei have passed to the periphery. Meanwhile the 
mitosis advances from prophase to metaphase. 
The oogonium in this condition presents typically a region 
of uniform finely vacuolate cytoplasm devoid of nuclei, sur- 
rounded by a zone of cytoplasm bearing large vacuoles and con- 
taining the nuclei in metaphase. This condition I have termed 
the stage of zonation (fig.3). A full understanding of this stage 
is necessary to interpret it in other species. Zonation presents 
the first clear differentiation of ooplasm from periplasm at a time 
previous to the existence of any wall between these parts, and 
finds the ooplasm nearly or quite devoid of nuclei. Zonation is 
very definitely and clearly marked in A. Bhi and A. Portulacae, 
the periplasm and ooplasm being as sharply separated as though 
an actual wall existed between them, but is much less conspicu- 
ous in A. Tragopogonis and A. candida, thus rendering these spe- 
cies more difficult of interpretation. ; 
Immediately following zonation the nuclei divide, many of 
them lying in such a position that one of their daughter nuclei 
reenters the ooplasm. In A. But nuclei are frequently found 
in late anaphase with one daughter nucleus lying inside of the 
oosphere and the other in the periplasm, thus affording direct 
evidence of the derivation of the primary oospheric nuclei. This 
rarely occurs in A. Portulacae, as the dividing nuclei usually lie 
quite outside of the line separating ooplasm and periplasm. The 
results, however, are precisely those presented in A. Bun, 
namely, one of the daughter nuclei of each mitotic figure, lying 
with its long axis approximately perpendicular to the boundary 
of the oosphere, reenters the ooplasm (figs. 4, Ss). 2 Re result- 
ing oosphere contains many nuclei, the number usually varying 
from 50 to 100 in this species. 
These primary oospheric nuclei now divide mitotically, and 
their products function as the female sexual elements. It should 
be carefully noted that there are here, as in A. Bliti, two mitoses 
in the oogonium. The first occurs during the differentiation of 
the oosphere and provides the primary oospheric nuclei. The 
second occurs in the oosphere (figs. 6, 7) and results in the 
