88 MICRO-ORGANISMS AND FERMENTATION. 



With the exception of a small number of doubtful forms, 

 amongst which Crenothrix may be named, the bacteria form 

 a fairly uniform group, exhibiting the same simple structure 

 and the same method of propagation throughout. It is an 

 interesting fact that amongst the lowest green plants, the 

 algae, there is a group which exhibits the same construction 

 and the same method of propagation as the bacteria, so that 

 the lowest green plants connect up with the lowest fungi. 

 It has already been mentioned that green plants possess the 

 power of absorbing and assimilating the carbon dioxide of 

 the air, owing to a special constituent of the cells, chlorophyll. 

 This power is not possessed by fungi, and the lowest group 

 of algse has been classified, therefore, under the name of 

 Schizo-algce, in contrast to the Schizo-fungi. It is not only a 

 physiological difference that distinguishes the two groups 

 that could not be used as the basis for a systematic classification 

 but rather that the structure of the cell contents is entirely 

 different, since the Schizo-algce contain grains of chlorophyll. 

 On the other hand, the Schizo-algce have not the power possessed 

 by bacteria of forming endogenous spores, but the method of 

 division exhibited by Crenothrix (see Fig. 31) frequently 

 occurs in the algae. To illustrate how difficult it is to define 

 strict limits in nature, it may be stated that there are undoubted 

 bacteria which contain green colouring matter, and yet others 

 that can assimilate atmospheric carbon dioxide. 



Most people are agreed that bacteria are to be classed 

 amongst the fungi, although, in their method of propagation, 

 they stand nearer to the algae. There are, however, fungi 

 which show the same kind of cell division as bacteria, and 

 even the remarkable formation of endospores also occurs 

 amongst many fungi, especially amongst those that will occupy 

 us next, the Saccharomycetes. 



We have seen that bacteria have points of contact, both 

 with the lowest forms of algae and also with the lowest forms 

 of fungi. It must also be noted that in so far as certain 

 bacteria move about with the help of cilia, a similar relation- 

 ship exists between them and the lowest group of the animal 

 kingdom (the flagellata), which again have other characters 

 in common with bacteria. 



