SPIROGYRA 



341 



is called a sexual spore, because two cells unite to form it. 

 The two cells which thus unite are called gametes and are 

 identical in all their parts. This spore, therefore, is known 

 as a zygospore (Greek, zy<ios, 

 yoke; spora, seed). In the 

 formation of a zygospore, the 

 cells are joined permanently and 

 a form of sexual reproduction 

 is present. 



As a zjrgospore, spirogyra can 

 live in a resting condition dur- 

 ing periods unfavorable to its 

 growth, as in winter or during a 

 drought. When conditions again 

 become favorable the zygospore 

 germinates and grows into a 



filament. The spirogyra is able to do the same things 

 which a pleurococcus does and has the same life 

 processes. 



Figure 366. - - Microphoto- 

 graph of Conjugating 

 Spirogyra. 



LABORATORY STUDY OF SPIROGYRA 



Notice : (1) the clear outer part called the cell wall ; (2) the mail 

 mass of the cell, a substance called cytoplasm. (This ran be seen easilj 

 by putting a strong sugar solution under the cover glass. The cytoplasD 

 draws away from the cell wall into a compact mass in the center of tin 

 cell.) (3) The darker portion of the nucleus, in <>r near the center 01 

 the cell. (This can be seen clearly by patting a drop of weak iodine 

 under the cover glass, using fresh material for this test.) (4) A spiral 

 band of green coloring matter, chlorophyll, containing bright spots. 



Examine spirogyra in a mass, floated out in water in a ulass oron ;■ 

 plate. Feel of it and observe that it is slimy. Note its color and delicai 

 After it has been in the sun for a lime, note the bubbles of gas entangled 

 in the spirogyra. which help to make it float With a microscope • 

 amine filaments which are joined in places by outgrowths from othei 

 filaments. Such filaments are said to be in conjugation. Draw the out 

 growing tubes, the emptj cell, ami the zygospore or zygote. 



