SECT. I 



CRYPTOGAMS 



337 



material. These Bacteria oxidise sulphuretted hj-drogen into sulphur, and store 

 the latter substance in the form of rounded granules within their cells, ultimately 

 oxidising it to sulphuric acid. 



Leptothrix ochracea, the so-called Iron-Bacterium, oxidises oxide of iron to the 

 liydrated oxide of iron which it accumulates in the sheaths of its filaments. It 

 occurs in ditches and swampy places in meadows. 



The zymogenous or fermentation Bacteria and the saprogenous or decomposi- 

 tion Bacteria are other saprophytic forms. The former oxidise or ferment carbo- 

 hydrates. The latter decompose nitrogenous animal or vegetable substances 

 (albumen, meat, etc.) with the liberation of ill-smelling gases. 



Thus Streptococcus {Leucoihostoc) mesaitcrioidcs (Fig. 245) causes fermentation of 

 beet-sugar. It forms large mucilaginous masses like frog-spawn, the bead-like 

 rows of cells being surrounded by a gelatinous investment. The acetic acid 

 bacteria (Fig. 246 a, b, c) oxidise alcohol to acetic acid. The transformation of 



c^ 





Fro. 241.;. — Bacteria of fermi'iitation. «-<-, Vinegar bacteria ; a, Bacillus aceti ; b, Bac. Pcistev. nanus : 

 '-■, Bac. Kiitzingianus; il, Bac. acicli Zadfci, lactic acid bacillus; e, Clostridium hutyricnin, 

 butyric acid bacillus ; /, Plcctridium paluclosum, fermentation bacterium from marsh water. 

 (From A. Fischer, Varies, iiber Bacterien, x 1000.) 



sugar into lactic acid is brought about by the rod -like cells oi Bacillus ccculi lactici 

 (Fig. 246, cl). ClosLrklmm bulyricum (Fig. 246, c) forms butyric acid from various 

 carbohydrates in the absence of oxygen, while certain marsh Bacteria (Fig. 246, /) 

 in the absence of oxygen form marsh-gas and hydrogen from cellulose. Bacillus 

 vulgaris is the most common cause of decomposition of meat, albumen, etc. 



The Purple Bacteria, M'hich develop in water with decomposing organic matter 

 in the absence of oxygen and the presence of light, contain, according to Molisch (•'), 

 a green and a red pigment (bacterio-chlorin and bacterio-purpurin). Other bacteria 

 secrete pigments in their cells or around them. The latter is the case with Bacillus 

 iwodiijiosus, the ellipsoid peritrichous rod-shaped cells of which form fuchsin-red 

 colonies on milk or bread, and so- have given rise to tlie miracle of the bleeding 

 Host. 



The photogenic bacteria pi'oduce within their cells a substance which becomes 

 phosphorescent on oxidation. The most widely sj^read of these phosphorescent 

 bacteria is Bacterium phos2}horeum, which occurs on meat. 



The parasitic bacteria inhabit joth animals and plants. The best known forms 

 which cause diseases of plants (bacterioses) are Pscudomonas Ryacinthi, giving rise 



Z 



