XI. 



LEPTOTRICHE^E AND CLADOTRICHE^E. 



ZOPF and other systematic botanists place among the bacteria cer- 

 tain microorganisms which are more interesting to the student of 

 general biology than to the pathologist, but which require description 

 in a manual of bacteriology. In our descriptions of the species in- 

 cluded by Zopf in the Leptotrichese and Cladotrichese we shall follow 

 the author named. Four genera are included in the LEPTOTRICHE^E, 

 viz.: Crenothrix, Beggiatoa, Phragmidiothrix, and Leptothrix. 

 The CLADOTRICHE^E are included in a single genus : Cladothrix. 



432. CRENOTHRIX KUHNIANA (Rabenhorst). 



Synonym. Brunnenfaden. 



Very common in running or in stagnant water. It sometimes develops 

 so abundantly in reservoirs and conduits of water that the water supply is 

 unfit for drinking or for certain industrial purposes. 



Morphology, In different stages of development appears as cocci, short 

 rods, and long filaments. The cocci are small spheres of from 1 to 6 p in 

 diameter ; the cell wall of these becomes gelatinous and they multiply by 

 binarv division, the gelatinous capsule of the daughter cell remaining en- 

 closed in that of the mother cell ; later they are set free by the solution of 

 this gelatinous envelope ; the zooglcea formed by these cocci are irregular in 

 form and may attain a diameter of one centimetre or more. These zooglcea 

 sometimes accumulate in enormous masses in reservoirs of water; at first 

 they are colorless, but later they are colored by hydrated oxide of iron and 

 appear brick-red, olive green, dark-brown, or brownish-black. When culti- 

 vated in swamp water these cocci grow out into rods, which by binary divi- 

 sion produce filaments ; these are seen projecting in all directions from the 

 zoogloea masses. When these reach a certain age they become segmented, 

 and the segments, enclosed in a common sheath, acquire a rusty-red or 

 dark-brown color from being impregnated with oxide of iron ; the rod-shaped 

 segments break up into spherical bodies which are comparatively large 

 (" macrococci ") ; some broad filaments, however, contain disc-like seg- 

 ments, which break up into smaller cocci. The rod-shaped and spherical 

 segments escape from the ruptured extremity of the common sheath. Some- 

 times the sheath becomes prematurely gelatinous, and the cocci and rods 

 remain in situ and germinate ; in this case they break through the gelati- 

 nous walls, and the original filament is seen to be surrounded by a brush- 

 like outgrowth of filaments. In these secondary filaments, as well as in the 

 primary, there is a distinct differentiation of the two extremities, growth 

 occurring at the free extremity and not at the base. The filaments are some- 

 times wavy or even spiral in form. 



Biological Characters not well determined, owing to the difficulty of cul- 



