336 



BOTANY 



PAKT II 



==/iV-;i/V:5^ ;^-«.;j».,. 



their respiration, and are therefore aerobic ; many can, however, develop without 



tliis gas, while some species, e.g. 

 the butyric acid bacterium and the 

 tetanus bacillus, are strictly an- 

 aerobic and only succeed in the 

 absence of oxj'geu. Some bacteria 

 produce by their respiration con- 

 siderable heat ; this is the explana- 

 tion of the spontaneous heating of 

 damp hay, dung, tobacco, and cotton- 

 wool. In such substrata Bacillus 

 calfactor develops ; it is adapted to 

 live at high temperatures (above 40°) 

 and is still motile at over 70° C. 

 (cf. p. 248). 



Saprophytic and parasitic species 



are distinguished, though a sharp 



separation is often impossible. In 



,^ . '\ ,^- . • ,•/:;' cultures the parasitic forms can be 



■'■<iS;jf. „ ,' ••^i;- made to lead a saprophytic life on 



'••..-.:";';. ^.,%*.t- ■::-,;.''" suitable substrata. 



- °' ' To the saprophytic Bacteria be- 



Fif;. 244. — Bacillus subtilis. a, d, Motile cells and long in the first place the forms 

 chain of cells ; b, non-motile cells and chains of ^y\^[^.\^ inhabit water. The widely 



distributed Cladotlirix dichotoma is 

 morphologically the highest among 

 these. It is found in stagnant 

 water, and consists of falsely branching delicate filaments attached to Algae, 

 stones, and woodwork, and forming a slimy coating over them ; the filaments 

 are composed of rod-shaped cells. Repro- 

 duction 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. 243). The swarm-cells 

 come to rest after a time and grow into 

 new filaments. 



Another very common form is Creno- 

 thrix KiUiniana, which consists of un- 

 brauched filaments attached to the sub- 

 stratum, but easily broken. It often forms 

 masses in the cavities of water-pipes, 

 blocking them up and rendering the water 

 undrinkable. The reproduction of Crcno- 

 tlirix is effected by small, round, non- 

 motile cells, whicli arise by subdivision of 

 the cells of a filament enclosed by its 

 sheath. 



The numerous kinds of Sulphur Bac- 

 teria, of whicli Berjijiatoa alba is the most 

 widely distributed, are found in sulpliurous springs and at the bottom of pools 

 where sulpliuretted hydrogen is being formed by decomposition of organic 



cells ; 0, spores from the zoogloea, e. (From A. 

 Fischer, Varies, iiber Baeterieii. a-d, x 1500; c, 

 X 250.) 



Fn;. •lAb.—Stre'ptocuixusviestnterioides. A, Iso- 

 lated cells without f^elatinous sheiith ; 

 B, C, formation of cliaiii of cells with 

 jjelatinons sheath ; D, portion of mature 

 zooi,'loea ; E, formation of isolated cells in 

 the lilaments of the zoogloea. (After Van 

 TiEOHEM, X 520.) 



