THE ALG 45 
of two kinds and one may have rebranched. The large round 
cell forms one large gamete—the egg or oosphere. The 
curved structure produces small gametes—the sperms. One 
sperm unites with the egg, thus forming a spore, called an 
oospore because it is formed by union of a sperm and an 
oosphere or egg. The oospore passes through a resting- 
period, and then reproduces the Vaucheria plant. 
The large cell being specially set apart to form an 
oosphere is called an oogonium. The curved structure that 
bears the sperms is called the antheridium. 
The process of union of the sperm and the egg—that 
is, union of dissimilar gametes, is known as fertilization. 
Draw an antheridium, an oogonium containing an 
oosphere or egg, and one with an oospore. How does the 
appearance of the oospore differ from that of an oosphere? 
General questions—Why is Vaucheria found in damp 
places only? Could Vaucheria live in direct exposure to 
strong light? Why? Why do the plants which are grow- 
ing deep in the aquarium elongate toward the light? Do 
you find separated antheridia and oogonia? What advan- 
tage in this arrangement? How is the structure of anther- 
idia and oogonia especially adapted to the work of fertiliza- 
tion? How do these reproductive organs differ in origin 
from those of plants before studied? In how many ways 
may Vaucheria reproduce itself? 
LESSON XL 
General study of Alge 
If in the vicinity there is a good representation of Alge, 
a general field study should be made of as many kinds as 
possible. The student should note the various types, where 
they live, and how their ‘structure is adapted to the place 
in which they live. Places visited at the time of the first 
lesson should be revisited and studied from the view-point 
