172 BOTANICAL GAZETTE [SEPTEMBER 
through the periplasm (fg. 97). Judging from this condition 
the terminal portion of the tube must vanish immediately after 
giving up its contents. The portion imbedded in the periplasm 
becomes thickened, resembling the primitive wall; but it seems 
never to attain the character of the mature epispore, asis the 
case in so many other species of Albugo, Indeed, no traces of 
the antheridial tube were ever seen in ripe spores. : 
The character of the ooplasm changes when the antheridial 
tube opens. As may be seen by comparing /ig. 70 with figs. 80, 
82, 84, 85 the vacuoles increase considerably in size and become — 
irregular in form. The most striking feature of this later condi- 
tion, however, is the tendency of the contents of the oosphere 
to break away from the periplasm (fig. 80), a phenomenon never 
met in younger stages. This indicates that changes have 
occurred at the boundary between the ooplasm and_periplast 
Indeed, it is at this time that a true wall may be first observed : 
around the oosphere. It will be remembered that previously ade 
periplasm and ooplasm were separated only by the delicate film | 
that appeared during zonation; but now for the first time adit 
tinct wall is present around the ooplasm, and its advent ee 
to be correlated with the opening of the antheridial tube. 
The wall occupies precisely the position of the film botnet 
the ooplasm and periplasm, and is probably formed by ah | 
development of that structure. Its intermediate position betwes! 
the ooplasm and periplasm and the apparent organic connie’ 
with both leads to the belief that it is the product of the ie 2 
action of both regions, rather than of either ooplasm a 
plasm alone. Since this wall remains perfectly distinct ch 
walls that are formed later, it will hereafter be called the 
tive wall. This term is used simply for convenienc’ . 
paper. Further study of related forms may esta att | 
homologies and lead to further classification. The 
wall is very clear and homogeneous in structure, €? hicknes 
striations, and shows great regularity of curve and - ee 
From this time on the condition of the developing walls 
as an index to the age of the oospore. 7 
