340 



BOTANY 



TAKT II 



111 addition to saprophytic and parasitic Bacteria, there are some which, 

 though possessing no chloroiihyll, obtain their food from inorganic compounds 

 only. These are the Nitrite Bacteria. {Nitrosomonas), and the Nitrate Bacteria 

 {Nitrohacter), which live in the soil. The former oxidises ammonia to nitrous acid, 

 and the latter oxidises the nitrous to nitric acid. They both obtain their carbon 

 from carbonic acid, and thus derive their food independently of any organic food- 

 supply (Fig. 249, cf. p. 245). 



The Myxobacteriaceae (") are a very peculiar family of Bacteria, our accurate 

 knowledge of which is in the first instance due to Thaxtek. They nearly all live 

 saprophytically on the dung of animals, and in habit resemble the Myxomycetes 

 (cf. p. 342). In the vegetative stage they appear as swarms of rod-shaped Bacteria 

 connected together by the gelatinous substance secreted by the cells, and exhibit 

 slow creeping movements. Ultimately they form fructifications that are usually 

 brightly coloured ; these have the form either of definitely limited masses of spores 

 or of cysts containing within a firm membrane the numerous bacterial spores. 

 The cysts are unstalked, or are raised singly or in groups on a stalk, formed, like 

 the wall of the cyst, of the hardened gelatinous material (Fig. 250). 



Class II 



Cyanophyceae, Blue-grreen Algae (') 



The Cyanophyceae are simply organised unicellular or filamentous 

 Thallophytes of a bluish-green colour; the cells or filaments are 

 frequently united, into colonies by the gelatinous swelling of the cell 

 walls. The numerous species, which are distributed over the earth, 



P'lo. '2i>1.—(lloeocnpsa polydermatica. 

 A, III process of division ; B, tu 

 the left, shortly after division ; 

 C, a later stage, (x 540.) 



i^s^fe 



Fiii. 252. — A, Oscillariu princcpn: a, terminal portion of a 

 lilaincnt; h and c, portions from the middle of a tilament 

 projieily lixed and stained ; I, cells in division (x lOSU). 

 B, OsclUarla Froelichii (x 540). 



live in water, or form gelatinous or filamentous growths on damp 

 soil, damp rocks, or the bark of trees. 



The protojilast of each cell possesses a peri]>hcral chroniatoi>hore of the form of 

 a liollow cylinder or hollow sphere ; in addition to chlorophyll this contains a 



