CLASSIFICATION 



83 



B 



The arthrospores are more resistant than the vegetative cells, and remain 

 after the rest of the plant is dead. On germination (Fig. 57, F, G) the contents, 

 after contracting somewhat, divide 

 once or twice by transverse walls, and 

 the outer spore-membrane is ruptured, 

 allowing the short filament to pro- 

 trude. It elongates and grows rapidly 

 until the new plant is complete. 



In Anabcena Azollce, the vegetative 

 cells may enter a resting-stage without 

 assuming the forms of definite spores, 

 simply separating and losing most of 



their color. When growth is resumed, 

 these cells develop chlorophyll again 

 and begin to divide and grow at once. 



Movements 



None of the true Schizophycese 

 have cilia, although blue-green 

 motile organisms, e.g. Crypto- 

 monas, Cryptoglena, are known; 

 but these are structurally quite 

 different from the typical Schi- 

 zophyceae. Goebel, however, 

 mentions having observed cili- (x 500). 

 ated cells in Merisinopoedia, one 

 of the Chroococcaceae, but they 

 have not yet been seen by other observers. 



The most striking movements are those of the Oscillatoriacese. 

 Oscillatoria is one of the commonest of the Sehizophycese, abound- 



A B C 



FIG. 57. A, B, C, Cylindrospermum 

 sp, spore; h, heterocyst 

 D, E, Anabsena Azollse. E, 

 cells in process of fission. F, G, germi- 

 nating spores of Cylindrospermum. 



FIG. 58. A, leaf of Myriophyllum with colonies of Glceotvichia natans, slightly 

 enlarged. B-D, development of the spore (X450). E, branching filament; 

 h, young heterocyst. 



ing in every fresh-water pool, and its movements have been repeat- 

 edly studied, but are still not clearly understood. The slender 



