36 CHLOROPHYCEAE 



with a living cell at the apex. An oblique division of the living cell 

 results in a branch being formed and sometimes one half may cease 

 to divide, thus leaving a living cell in the middle of the dead cells. 

 It is evident from a consideration of this process that at each divi- 

 sion a potential swarmer is formed which is not normally liberated. 

 On the few occasions when it is freed then the species is perpetu- 

 ated, but at present the particular conditions under which a swarmer 

 may be liberated are not known. 



REFERENCES 



Eudorina. Akehurst, S. C. (i934)- J- ^oy. Micr. Soc. 54, 99. 



Cytology. Chaudefaud, M. (1936). Rev. Alg. 8, 5. 



Sphaerella. Elliott, A. M. (1934). Arch. Protistenk. 82, 250. 



Tetraspora. Geitler, L. (1931)- Biol. Zbl. 51, 173. 



Gonium. Harper, R. A. (191 2). Trans. Amer. Micr. Soc. 31, 65. 



Eudorina, Gonium. Hartmann, M. (1924). Arch. Protistenk. 49, 375. 



Prasinocladus. Lambert, F. D. (1930)- ^' Bot. 23, 227. 



Volvox. Lander, C. A. (1929). Bot. Gaz. 87, 431. 



Flagellae. Petersen, J. B. (1929). Bot. Tidsskr. 40, 373. 



Volvox. PococK, M. A. (1933)- Ann. S. Afr. Mus. 16, 523. 



Volvox. PococK, M. A. (1938). jf. Quekett Micr. Club, ser. 4, i, i. 



Pleodorina. Shaw, W. R. (1894). Bot. Gaz. 19, 279. 



Eudorina, Gonium. Smith, G. M. (1930-1). Bull. Torrey Bot. Club, 57, 359. 



Volvox. Zimmerman, W. (1921). Jb. wiss. Bot. 60, 256. 



Chlamydomonas. Behlau, J. (1939). Bei. Biol. Pfianzen, 27, 221. 



Eudorina. Doraiswami, S. (1940). jfourn. Ind. Bot. Soc. 19, 113. 



CHLOROCOCCALES 



This is an order which is probably of polyphyletic origin but it is 

 not proposed to elaborate this problem here. 



*=Chlorococcaceae: Characium (a slip or cutting). Fig. 26. 



Each plant is a solitary unicell and only possesses a motile re- 

 productive phase, and it may be supposed that in some previous era 

 the vegetative phase ceased to be motile and became attached. The 

 ellipsoidal cells occur singly or in aggregates on submerged plants 

 or living aquatic larvae, being borne on a short stalk which emerges 

 from a small basal disk. Asexual reproduction is brought about by 

 means of biflagellate zoospores which are liberated through a 

 terminal or lateral aperture. Certain species exhibit anisogamy, 

 whilst in C. saccatum the sexual and asexual generations are distinct 

 so that there may therefore be two different cytological generations. 



