420 BOTANICAL GAZETTE [DECEMBER 
center. After this stage, there are a few free nuclear divisions 
at the base of the egg before walls begin to appear, and at the same 
time amitotic divisions may take place in the upper portion. 
CovuLTER and CHAMBERLAIN (4) found in Zamia floridana a 
somewhat different condition. After about eight simultaneous 
free nuclear divisions, giving rise to 256 free nuclei, walls appear 
at the base of the proembryo, just as in the formation of endosperm 
in most angiosperms, but no vacuole is developed. 
SAxTON (9) has recently described some of the later stages in 
the embryo of Encephalartos. He finds that the suspensor is a 
root cap, and that the embryogeny is very similar to that of Ginkgo. 
DIOON,; FREE NUCLEAR PERIOD 
In Dioon edule fertilization is followed immediately by a long 
period of simultaneous, free nuclear division. The first mitosis 
of the fusion nucleus occurs in the position where fertilization has 
taken place, a little above the middle of the egg, the spindle being 
oblique, as is usually the case in gymnosperms. The succeeding 
mitoses follow rapidly, and the nuclei, even as early as the 16- 
nucleate stage, become rather evenly distributed throughout the 
entire proembryo. Occasionally the nuclei move toward the bot- 
tom of the proembryo, the 16, 32, and 64-nucleate stages having 
been found with all the nuclei below the middle of the proembryo, 
and in one case a 64-nucleate stage had all the nucleiin the lower 
third. On the other hand, two 4-nucleate stages were observed 
with all the nuclei above the middle of the proembryo. 
In stages following the 64-nucleate stage—resulting from the 
sixth mitosis—the number of nuclei in the lower part of the pro- 
embryo is likely to be considerably larger than that in the upper 
part. At the 128 and 256-nucleate stages—resulting from the 
seventh and eighth mitoses—the larger number at the bottom 
is due to a settling of the nuclei; but at the ninth mitosis some of 
the nuclei in the upper half of the proembryo may fail to divide, 
and thus add to the disproportion. It may happen, occasionally, 
that the ninth mitosis, which gives rise to the 512-nucleate stage, 
may be the last of the simultaneous divisions; but usually there 
is a tenth mitosis, which would give rise to 1024 nuclei, if all nuclei 
