VAUCHERIA 95 



3. Stain with iodine. Is starch present ? 



4. Material stained with hsematoxylin and mounted in balsam will 

 show the very numerous minute nuclei. The filaments are there- 

 fore coenocytes (see Principles, Sec. 229). 



B. In fruiting material study and draw the sexual organs, vari- 

 ously grouped in different species. 



1. The large oval, female organ, or oogonium, sessile on the 

 parent filament but separated from it by a wall. The pro- 

 toplast becomes a naked egg within the oogonium, which 

 forms a pore (for the entrance of sperms) in a short, beak- 

 like structure somewhat at one side near the tip. 



2. The mature oospore, with its heavy wall, developed from 

 the fertilized egg. Note the changed appearance of the con- 

 tents of the oospore, now rich in food material. 



3. The male organ, or antheridium, at the end of a short 

 branch bent like a crook, and separated by a wall from 

 the parent filament. It develops a very large number of 

 minute two-ciliate sperms. 



Because the form or morphology of these gametes is unlike, 

 this type of sexual reproduction is called heterogamy. 



C. Allow material to remain in a vessel of water. It may form 

 zoospores.^ If so, note : 



1. Their large size and habits of germination. If studied 

 when motile, observe their slow swimming. Stain the zoo- 

 spores with iodine to show the very numerous delicate cilia 

 all over the surface ; these are really pairs of cilia, each 

 pair above a nucleus (see Principles, Fig. 189, C). Draw. 



2. The formation of the zoospores at the tips of filaments 

 which appear darker in color. Note the cross wall cutting 

 off a terminal sporangium, the protoplasm of which becomes 

 the single zoospore. Draw. 



3. Stages in the germination of the zoospore and the devel- 

 opment of the sporelings. 



1 Material of Yaucheria is likely to produce zoospores in large numbers if placed 

 in fresh water after some days of cultivation in five per cent Knop's solution 

 (Sec. 200, A). 



