334 



BOTANY 



is a very simple one. the individual species, which can often be barely dis- 

 tinguished by morphological characters, show great variety in their metabolic 

 Miid in their mode of nutrition. The majority of Bacteria require 

 oxygen for their respiration, and are 

 therefore aerobic; many can, however, 

 develop without this gas, while some 

 species, e.g. the butyric acid bacterium and 

 the tetanus bacillus, are strictly anaerobic 

 and only succeed in the absence of 

 oxygen (cf. p. 242). 



Saprophytic and parasitic species are 

 distinguished, though a sharp SI-JIM rat ion 

 is often impossible. In cultures the para- 

 sitic forms can be made to lead a sapro- 

 phytic life on suitable substrata. 



To the saprophytic Bacteria belong in 



Fio. 255. IiucoiMMtoe nusenterioide*. A, Iso- 



the first place the forms which inhabit 



. . . , - , ., , ,. ., , , /-, , 



feted .,-lls without gefetbuma sheath; water " The Wldel y distributed Clado- 

 B, C, formation of chain of cells with tkritS dichotoma is morphologically the 

 gelatinous sheath ; D, portion of mature highest among these. It is found in 

 zoogloea ; K, formation of isolated cells in stagnant water, and consists of faldv 

 the filaments ofthezoogloea. (After VAN branchi delicate filaments attached to 

 Hi:.. HEM, X 520.) 



Algae, stones, and woodwork, and forming 



a slimy coating over them ; the filaments are composed of rod-shaped cells. 

 Reproduction is effected by ciliated swarm-cells, which originate by division 

 from cells of the filament and are -set free by the swelling of the sheath (Fig. 

 253). The swarm-cells come to rest after a time and grow into new filaments. 



Fio. 256. Bacteria of fermentation, u-c, Vinegar bacteria ; , LV /'<" . /'<>.*.' 



c, Bac. Kutzin guinus; d, Bac. addi lactici, lactic acid bacillus ; e, Clostriiiimn imtiti-ii-iim, butyric 

 acid bacillus; /, Plectridium paludogum, fermentation bacterium from marsh \vutt-r. (I-'miii 

 A. FISCHER, Varies, uber Bacterien, x 1000.) 



Another very common form is Crenothrix Kuhniana, which consists of un- 

 branched filaments attached to the substratum, but easily broken. It often 

 forms masses in the cavities of water-pipes, blocking them up and rendering tin- 

 water undrinkable. The reproduction of Crenothrix is effected by small, round, 



