444 



PROTOPHYTA 



such as O. princeps (Vauch.), the diameter is much greater, the separate 

 filaments, just visible to the naked eye, floating on the surface of the 

 water. Lyngbya Ag. is distinguished by its property of forming 

 ' persistent cells,' the function of which is not known ; they may possibly 

 be propagative spores. The species have a much less active motion than 

 those of Oscillaria, and chiefly inhabit salt or brackish water. Symploca 

 Ktz. grows in tufts, frequently among grass with the habit of a Rivularia. 

 In Microcoleus Desm, and Inactis Ktz. a large number of filaments are 

 enclosed in the same gelatinous sheath. 



The genera Chamaesiphon (A. Br.), Clastidium (Kirch.), Cyanocystis 



(Bzi.), and Dermocapsa (Crouan) (to 

 which Thuret adds Xenococcus and 

 Sphaerogonium, Rostaf.) constitute 

 Borzi's family of Chamasipkona&a, dis- 

 tinguished, according to that author, 

 by the presence of coccogones, propa- 

 gative cells of the nature of sporanges, 

 in which conids are formed by repeated 



FIG. 370. Spirulina tenuissima Ktz. 

 ( x 400). (After Cooke.) 



FIG. 371. Lyngbya (estuarii Liebm. (x 2co). 

 (After Hauck.) 



division, the usual number in each coccogone being four, eight, or 

 sixteen. Clastidium (Jahrhft. vaterl. Naturk. Wiirtemberg, 1880, p. 135) 

 is characterised by each filament having a terminal bristle. Dermocapsa 

 and Xenococcus are epiphytic on Catenella, Lyngbya, and other marine 

 algae. The former genus has been placed among both Florideae and 

 Fucaceae, owing to its mode of propagation ; D. violacea (Crouan) has 

 a bright red colour. 



Plaxonema Tangl (Sitzber. Akad. Wiss. Wien, 1882) is a fila- 

 mentous protophyte with the habit of an Oscillaria, but characterised by 

 the presence of a disc-shaped chromatophore in the blue-green proto- 

 plasm. Under certain conditions the filaments break up into zoogloea- 

 like colonies. J3orziaCo\\n (Jahrber. Schles. Vaterl. Cultur, 1883, p. 226) 

 is a genus of Oscillariaceae with the habit of a bacillus, consisting of 



