CHLOROPHYCEAE 



215 



unfavorable. Look where you find Sphagnum, Vaucheria, Alisma, 

 Equisetum fluviatile, Utricularia, Typha, and Chara. Dr. Nieuwland 

 reports that Pandorina, Eudorina and Gonium are commonly found 

 in summer as constituents of the green scum on wallows in fields where 

 pigs are kept. The flagellate, Euglcna, is often associated with these 

 forms. If you have a culture in the laboratory, do not throw it out 



Contractile Vacuo/e 

 Nucleus 

 \ Eye spot 



Pyrenoid 



Nucleus 

 ■Pyrenoid 



Diagram of Vegetative Reproduction 



Diagram Gametic Reproduction 



Fig. 43. — Chlamydomonas: A, vegetative cell of the zoospore; B, the zoospore loses its cilia and 

 rounds off; C, four new zoospores are formed within the parent zoospore; D, when eight new indi- 

 viduals are formed within the parent zoospore, the eight are gametes. X 1,000. The second and 

 third rows are diagrams of vegetative and gametic reproduction. Vegetative reproduction: 1, 

 zoospore; 2, zoospore has lost its cilia and rounded off; 3, the rounded cell is dividing; 4, the rounded 

 cell has divided, producing four zoospores; 5, the rounded cell instead of dividing as in 3 and 4 has 

 produced four zo5spores within itself; 6, the four zoospores have escaped from the rounded cell. 

 Gametic reproduction: 1, zoospore; 2, the zoospore has lost its cilia and rounded off; 3, eight gam- 

 etes are formed inside the rounded cell; 4. gametes escaping; 5, two gametes uniting; 6, zygote 

 formed by the two uniting gametes; 7, four zoospores escaping from the germinating zygote. From 

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



when the culture disappears, because new coenobia are likely to de- 

 velop from the oospores. 



Many fixing agents cause the protoplasmic connections between the 

 cells to be withdrawn. Figure 44 ^, showing the protoplasmic connec- 

 tions in nearly the living condition, was drawn from material fixed in 

 the hot aqueous corrosive sublimate-acetic acid solution; B, fixed in a 

 1 per cent chromo-acetic solution, does not show the connections; C 

 to E show details drawn from sections. 



For paraffin sections, the material, preferably in sufficient abund- 

 ance to make a layer 5 mm. deep may be placed in a shell with a bot- 



