414 



PROTOPHYTA 



Sykidiony^Yi^X. (Trans. Irish Acad, 1881, p. 27) is also a marine genus, 

 allied to Characium and Hydrocytium ; but the zoospores escape 

 through a terminal instead of a lateral fissure. 



Of free-swimming forms occurring in fresh water, Nephrocytium 

 Nag. consists of kidney-shaped gonids enclosed 

 in a hyaline envelope. Although the production of 

 zoospores has not been detected in this genus, its 

 position is probably here, though its true place 

 may possibly be among the Sorastreae. Dangeard 

 (Bull. Soc. Linn. Normandie, i., 1888, p. 196) has 

 observed a mode of propagation by the formation 

 of daughter-colonies within the membrane of the 

 parent-colony. In Ophiocytium Nag., the origi- 

 nally cylindrical individual becomes curved in a 

 serpentine manner, and produced at one extremity 

 into a hyaline spine. The zoospores escape by the detachment of the 

 cap-like apex of the hyaline envelope. 



In Hormospora Breb. the free-swimming individual or colony con- 

 sists of a very elongated straight or bent cylinder, sometimes branching, 

 the gonids arranged in a single or double row within a dense hyaline 

 envelope. No formation of zoospores has been observed. Cylindro- 

 capsa (Reinsch) (see p. 227) is placed here by some authorities. 



Fig. 343. — Nephrocyiiuin 

 Ndgelii Grun. ( x 300). 

 (After Cooke.) 



Fig. 344. — Hon7WSpora-tmitabilis^'c€a.i^y. 2cx)). (From nature.) 



Although in the majority of the genera named above only one kind 

 of swarm-spore has hitherto been observed, it is highly probable that 

 some or all of them produce both megazoospores and zoogametes with 

 a sexual function. 



Literature. 



Fresenius — Abhandl. Senckenberg. Naturf. Gesell., iii., 1856-8, p. 237. 



Archer — Microscop. Journ., 1866. 



Zukal — Oesterr. Bot. Zeitschr., 1880, p. 11. 



Holmes — Joum. Linn. Soc, xviii., 1881, p. 132. 



Borzi — Nuov. Giorn. Bot. Ital., 1882, p. 272 ; and Studi Algologici, 1883. 



Lagerheim— Bot. Centralbl., xii., 1882, p. 33 ; and Oefv. Vetensk. Akad. Fdrhandl., 



Stockholm, 1885, p. 21. 

 IClebs — Unters. Bot. Inst. Tiibingen, i., 1883, p. 233. 

 Bennett — ^Journ. Micr. Soc, 1887, p. 9; and 1888, p. 2. 



