CHLOROPHYCEAE 



233 



gating, the awkward, jerky movements of the pair contrast sharply 

 with the graceful movements of the zoospores. 



Fix in chromo-acetic acid— 1 g. chromic acid and 2 c.c. acetic acid to 

 100 c.c. water ; or in 0.7 g. chromic acid— 3 c.c. acetic acid, and 6 c.c. 1 per 

 cent osmic acid to 100 c.c. water. Formalin-acetic acid— 10 c.c. for- 

 malin and 5 c.c. acetic acid to 100 c.c. water— is a good fixing agent, 

 especially when followed by phloxine and aniUn blue. The anilin blue 



m 



^ 1 M 



A B C D F G 



Fig. 5.5. — Ulothrix: A, part of vegetative filament. B, a vegetative cell at the top; the cell be- 

 low has divided and one more division would make 4 zoospores; the next cell shows 4 young zoo- 

 spores, and the bottom cell has 4 zoospores almost ready to escape; e, eye spot; n, nucleus; p, py- 

 renoid. C, each cell with 8 nearly mature zoospores. D, mature zoospore. £, filament with gametes. 

 F, two gametes uniting. G, zygote formed by the two uniting gametes. X535. From Chamberlain's 

 Elements of Plant Science (McGraw-Hill Book Co., New York). 



should stain the chromatophore and the phloxine the pyrenoids. Iron- 

 alum haematoxylin should stain the chromatophore gray and the 

 pyrenoids black. Mount on each slide material from both lots. 



Oedogonium. — Most species are found in quiet waters, especially in 

 ponds and ditches. The best fruiting material is often attached to sub- 

 merged twigs, rushes, and various plants, where, to the naked eye, it 

 forms only a fuzzy covering. Some species form floating masses, bear- 

 ing some resemblance to Spirogyra, but they are not so slippery. 



The fixing agents mentioned for Ulothrix are good for Oedogonium. 

 The iodine solution used in testing for starch, or a weak aqueous solu- 



