96 BOTANICAL GAZETTE [avcust 3 
group characterized by its very modern features (Cupressineae). 4 
While phylogenetic continuity of multiple sperms might be claimed q 
for Cycadales, no such claim could be maintained for Cupressineae. : E 
The greatest epoch in the history of the male gametophyte of 
gymnosperms, however, was the abandonment of ciliated sperms, 4 
and this occurred in connection with the establishment of Coniferales. — 
It is not generally appreciated that five of the seven recognized pri- = 
mary groups of gymnosperms possess ciliated sperms, and that the 3 
modern type or completely’terrestrial type of sperm was introduced by — 
the conifers. This also affected the pollen chamber, the pollen tube, ~ 
and the cell generations in spermatogenesis. The pollen chamber 4 
disappeared; the pollen tube ceased to be exclusively a branching — 
haustorial organ and became a sperm-carrier; while the last cell- 
generation in spermatogenesis was omitted. It is this condition of a 
spermatogenesis that is carried forward by angiosperms to a still 
greater stage of reduction. Just what cells are eliminated and what 4 
cells remain is a question of small importance. The significant fact a 
is that spermatogenesis is shortened, and the ultimate cells, although 
non-ciliated, are physiologically sperms. 
THE EMBRYO 
The absence of embryos from the seeds of Paleozoic gymnosperms — 
indicates that some great change connected with embryo-formation 
was introduced by the Mesozoic gymnosperms. It would be of 
extreme interest to know the ancient condition, but we know only 
what it has become. After this change, whatever it may have been, 
the proembryo has become the structure showing steady and pe 
gressive change. a 
The first stage in the development of the proembryo is free nuclear : 
division, followed by wall-formation; and in the most primitive 9 
condition the free nuclei are so numerous that wall-formation results ag 
in a tissue which fills the egg. The tendency is to reduce the numbet — 
of free nuclear divisions, resulting in a reduction of the amount of 3 
proembryonic tissue, so that more and more of the general cytoplasm : 3 
of the egg is left free from tissue. The proembryo of Ginkgo has is 
retained a very primitive character; and illustrations of early stag® _ 
in the reduction of the proembryo may be observed among the cycads: 2 
ne 
