July 1904 
Elementary Mycology 
179 
To this is given the name of zygospore (yoke spore) because 
formed of two similar gametes. In case of some of the Mildews, 
the Albugo (“White Rust”) of the Shepherd’s purse, etc., the 
sexual process differs from the above mainly in the fact that the 
two parts or organs producing the gametes are quite unlike each 
FIG. 14 
Fig. 14. Oospore formation in the so-called “ White Rust ” of the Conciferce, Albugo 
candidus (Alb.). Conidia (Con.) of this species are also shown at the right. An early 
stage of the Oogonium (Oog.) is figured, followed by its feotilization by the Antherid- 
ium (An.). The mature Oospore is represented (Oosp.). 
other (Fig. 14). The larger, or egg-cell, is designated as the 
oogonium , and the smaller one, or sperm-cell is called the anthe- 
ridium. The sexual spore in this case is called the oospore. The 
spore may have, in case of other groups, a mass of adjacent cells 
more or less completely enclosing it, developed simultaneously 
with the fusion of the nuclei or immediately before or after, the 
resulting structure suggesting a fruit — and hence such spores are 
called, carpospores. 
The Evolution and Purpose of Sexuality. — An exam¬ 
ination of the probable origin of sexual reproduction in the veg¬ 
etable kingdom may possibly indicate its purpose or advantages. 
Reference has already been made to swarm-spores — protoplas¬ 
mic bodies destitute of a cell wall and furnished with a cilium, 
or two or more cilia, that serve the purpose of locomotion through 
water. When these zoospores escape from the parent cell they 
swarm vigorously for an hour or more and then come to rest. 
Now it might happen occasionally in such apparently aimless 
motions that two of the cells would collide, perhaps fuse, and 
thenceforth act as a single cell; such has actually been observed 
to take place. That it merely “happens” so is indicated by the 
fact that most of the cells do not so collide and fuse, but each 
nevertheless develops independently into a new plant. If now 
anything in the way of vigor or other qualities proves valuable 
in such fortuitous union, the union of energies (that could never 
be absolutely identical in two separate masses!) might be a great 
