302 ALG^E 



these resting-cells have lain for some time dry, and then again been 

 flooded, the contents breakup into four or eight zDospores, which invest 

 themselves with a cell-wall, and, in the course of a single day, divide, by 

 successive bipartitions, into an eight-celled coenobe, which again, during 

 the next night, gives birth to eight motile families. The enclosed 

 primordial cells of Stephanosphaera are of a bright green colour, fusi- 

 form, and are attached to an equator of the investing membrane at 

 both ends by branched strings of protoplasm. The whole family 

 rotates on an axis at right angles to the plane which passes through 

 them all. 



In Gonium Mull, the ccenobe is a tabular aggregation of cells moving 

 rapidly through the water by the aid of vibratile cilia. Its life-history 

 has not been fully followed out, and very little is known of its mode of 

 reproduction. 



LITERATURE. 



Henfrey Trans. Micros. Soc. , 1856, p. 49. 



Cohn& Wichura (Stephanosphtera) Nova Acta Acad. Nat. Cur., xxvi. , Suppl. 1857, 



p. i (Quart. Journ. Micros. Sc., 1858, p. 131). 

 Archer Quart. Journ. Micros. Sc., 1865, pp. 166, 185. 

 Cienkowski Bot. Zeit., 1865, p. 21. 



Pringsheim Monber. Berlin Akad. , 1869, p. 721 ; and Bot. Zeit., 1870, p. 265. 

 Yolten Bot. Zeit., 1871, p. 383. 



Rostafinski - Bot. Zeit., p. 785 ; and Mem. Soc. Sc. Nat. Cherbourg, 1875. 

 Goroshankin Nachr. Gesell. Naturf. Moskau, 1875. 

 Hieronymus - Oesterr. Bot. Zeitschr., 1874, p. $i$etseq, 

 Reinhard- Arbeit. Naturf. Gesell. Charkoff, 1876. 

 Breal-Bull. Soc. Bot. France, 1 386, p. 238. 

 Dangeard (Chlamydomonas) Ann. Sc. Nat., vii., 1888, p. 105. 



ORDER 5. SORASTRE^. 



In this order are included a few genera distinguished by the ccenobe 

 being unciliated. In Sorastrum Ktz. the colony consists of a more or 



FIG. 264. Sorastrum spinu- 

 losum Nag. ( x 400). (After 

 Cooke.) 



FIG. 265. Ccclastrum citbicitm Nag. 

 (x 600). (From nature.) 



less spherical aggregation of closely-packed, horned or bind, somewhat 



