242 Campbell. — On the development 
granules, it often contains others that are not colored blue by 
the action of iodine. It is surrounded by a very delicate 
membrane that in some cases shows a bluish tint when treated 
with iodide of potassium. 
Not infrequently the spermatozoid becomes entirely free 
from the vesicle, and then its coils separate and the spiral 
becomes elongated. This is always the case with those found 
about the open archegonium, the vesicle being held fast in the 
mucilaginous matter about its opening. The spermatozoids 
are often held in the mucilage in which the macrospore is 
imbedded, so that often one sees hundreds about the macro- 
spore, not only in the vicinity of the open archegonium, but 
about the whole spore. It is true that the number is greatest 
about the open archegonium, which frequently becomes com- 
pletely choked up with them ; but only one reaches the 
oosphere, which thereupon becomes clothed with a cell-wall so 
as to effectually prevent the further entrance of spermatozoids. 
The basal walls of the neck-cells quickly turn brown, as an in- 
dication that fertilization is effected. Under normal circum- 
stances it seldom happens that an archegonium fails to become 
fertilized. 
In one case free spermatozoids were observed thirty-five 
hours from the time the spores were placed in water, but 
ordinarily from five to ten hours longer were necessary. 
The Macrospore and Female Prothallium. 
The structure of the macrospore of Pihdaria has been so 
thoroughly studied, that no attempt will be made here to give 
more than a brief outline of the same. The spores are oval 
in form and white in color, quite large enough to be readily 
seen with the naked eye. About one-third the distance from 
the top is an evident constriction, above which the diameter 
of the spore is noticeably greater. 
As already shown by the researches of Hofmeister 1 , Stras- 
1 Hofmeister, Vergleichende Untersuchungen, 
