SECT. I 



CRYPTOGAMS 



335 



non-motile cells, which arise by subdivision of the cells of a filament enclosed by 

 its sheath. 



The numerous kinds of Sulphur Bacteria, of which Beggiatoa alba is the 

 most widely distributed, are found in sulphurous springs and at the bottom of 

 pools where sulphuretted hydrogen is being formed by decomposition of organic 

 material. These Bacteria oxidise sulphuretted hydrogen into sulphur, and store 

 the latter substance in the form of rounded granules within their cells (cf. p. 243). 



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

 the hydrated oxide of iron which it accumulates in the sheaths of its filaments 

 (cf. p. 243). 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 Leuconostoc mesenterioides (Fig. 255) causes fermentation of beet-sugar. 



FIG. 257. Pathogenic Bacteria, u, Pus cocci ; h, erysipelas cocci ; c, gonorrhoea cocci ; (/, splenic 

 fever bacilli ; e, tetanus bacilli ; /, diphtheria bacilli ; g, tubercle bacilli ; h, typhoid bacilli ; I, 

 colon bacilli ; fc, cholera bacilli. (Prom A. FISCHER, Fortes, uber Bocterien, x about 1500.) 



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. 256 

 a, b, c) oxidise alcohol to acetic acid. The transformation of sugar into lactic 

 acid is brought about by the rod-like cells of Bacillus acidi lactici (Fig. 256 d). 

 Clostridium butyricum (Fig. 256 e) forms butyric acid from various carbohydrates 

 in the absence of oxygen, while certain marsh Bacteria (Fig. 256 /) in the absence 

 of oxygen form marsh-gas from cellulose. Bacillus vulgaris is the most common 

 cause of decomposition of meat, albumen, etc. 



The photogenic bacteria produce within their cells a substance which becomes 

 phosphorescent on oxidation (cf. p. 246). The most widely spread of these phos- 

 phorescent bacteria is Bacterium phosphoreum, and occurs on meat C 59 ). 



The parasitic bacteria inhabit both animals and plants. The best known 

 forms which cause diseases of plants (bacterioses) are Pseudomonas Hyacinthi, 

 Bacillus phytophthorus, which attacks the potato, and Bacillus Oleae, which gives 

 rise to the Canker of the Olive Tree ( 3 ). 



The numerous pathogenic Bacteria are the most important causes of infectious 

 diseases. Their injurious influence on the tissues and blood of men and animals 

 is brought about by the excretion of poisonous substances, to which the name 



