SECT. I 



CRYPTOGAMS 



311 



their cells if sulphuretted hydrogen he present in their environment. Another 

 filamentous Fission-Fungus, Crenothrix Kibhniana, in the sheaths of whose filaments 

 deposits of hydrated oxide of iron are found, is of frequent occurrence in springs and 

 water-pipes, where it forms brown slimy masses and renders the water unfit for 

 drinking. In both of these last-named Schizomycetes the filaments, unlike those of 

 Cladothrix, are unbranched. 



The majority of Bacteria, like these important water-bacteria, maintain a 

 saprophytic mode of life. Their metabolic processes vary in correspondence with 

 their numerous decomposition products, and are usually adapted to definite conditions 

 of nutrition. Thus the Hay bacillus, Bacillus subtilis, develops in an infusion of 

 hay. The spores are able to withstand the heat employed in making the infusion, 

 and produce in from 12 to 15 hours, on the surface of the liquid, a gelatinous pellicle 

 consisting of closely compacted parallel filaments. Each filament is composed of 

 long rod-shaped cells in active process of division (Fig. 230, A). After exhaustion 

 of the nutrient substance of the infusion, an endogenous formation of spores takes 



3 



A 



*™ in 



Fio. 230.— Bvcillns subtilis. A, Pellicle of parallel filaments (x 500) ; B, formation of spores 



(X 800). 



place within the cells of the filaments (B). In germinating, the walls of the spores 

 become ruptured on one side and their elongating protoplasmic contents emerge as 

 rod-shaped swarm-spores provided with numerous fiagella (Fig. 228), and multiply 

 further by division. 



Many saprophytic Bacteria are characterised by their capacity to induce ferment- 

 ation and putrefaction, and in the operation of their metabolic processes are able to 

 decompose certain organic compounds. Thus Lcuconostoc mesenterioides occasions 

 the mucous fermentation of beet -sugar. It forms gelatinous masses resembling 

 frog -spawn, consisting of a number of polygonal colonies enclosing rosary -like 

 chains of cells within the mucilaginous sheaths (Fig. 231, D). In its mode of 

 spore-formation this species of Fission-Fungus closely resembles the Fission- Algae 

 Nostoc. Special cells of the chain become larger and transformed into arthrospores 

 {E). In the process of germination these spores become invested with a gelatinous 

 sheath (_B), and develop into thick but short rows or chains of cells (0). These 

 unite into colonies, and these again into groups of colonies, thus forming large 

 gelatinous masses similar to the original. The Vinegar bacterium, Bacterium aceti, 

 oxidises alcohol into vinegar ; Bacillus amylobacter occasions the butyric fermenta- 

 tion ; Bacterium termo the putrefaction of albumen, meat, etc. 



