72 A LABORATORY MANUAL OF BOTANY 
the purpose of reproducing the plant. Any such specialized 
cell is a spore, though such cells may differ considerably in 
the manner of their formation. Spores formed, as this one, 
by the yoking together of two cells similar in size, are known 
as zygospores, which means “ yoke-spores.” The masses of 
protoplasm which unite to form spores are known as gametes, 
and the process of uniting similar gametes is known as con- 
jugation. 
Study favorable Spirogyra material, and draw the fol- 
lowing stages in its reproduction, being careful to label 
properly the different structures concerned in the process: 
(a) Where two plants are placed side by side and the 
cells of one are beginning to send out protuberances to meet 
similar protuberances from the cells of the other plant. 
(6) Where protuberances have united to form a tube. 
(c) Where one gamete is passing through the tube. 
(d) Completed zygospores ready for resting period. 
General questions.—Is the vegetative structure of Spiro- 
gyra more or less complex than that of plants already stud- 
ied? In what respects? Of what advantage to the plant 
is this heavy-walled resting-spore? Of what advantage to 
have the protoplasm of two cells unite to form this spore? 
Is this vegetative production? When several cells from two 
plants conjugate in pairs, does one plant always contain all. 
the ripe zygospores? Does one cell ever conjugate with more 
than one other cell? 
LESSON XXXVITII 
Cladophora ! 
General study.—Cladophora, an alga of very wide distri- 
bution, is found in both running and standing water, and is 
usually attached to some object that serves to anchor it. 
1Jf Ulothrix is to be had it should be introduced at this point, or 
any zoospore-forming plant may be used. 
