30 THE ORGANISMS OF FERMENTATION. 



algae (N'ostoc, Chroococcus, Merismopedia, Oscillaria, tyc.) into 

 one group, which, from their common and characteristic property 

 of reproduction by fission, he called Scliizophytce (fission plants), 

 and set up as an independent division. 



25. Assimilation of Carbon Dioxide without the 

 Aid of Chlorophyll. 



The classificatory basis for arranging the Thallophytes under 

 the two groups Algoe, and Fung), viz., the presence or absence of 

 chlorophyll, is not of a morphological, but of a physiological 

 nature, as its connection is not with the form, but with the vital 

 activity of the cell. Now, it has been proved by much research 

 that chlorophyll plays an important part in the life of green 

 plants. The chlorophyll in the cells, aided by sunlight, splits up 

 the carbon dioxide which the plant has absorbed from the air. 

 The oxygen of the C0 2 is exhaled, whilst the carbon is retained 

 and utilised in the elaboration of the various organic substances 

 of which the body of the plant is composed. This operation is 

 known as the assimilation of carbon dioxide. Until recently, 

 the opinion was generally held that this process could not go on 

 without the assistance of light and chlorophyll, and as the fungi 

 are, without exception, devoid of the last-named substance, it has 

 been laid down as a law that the fungi are incapable of assimi- 

 lating carbon dioxide and of constructing their cells of inorganic 

 substances like the algse do. The researches of Winogradsky 

 have, however, shown that there are fission fungi capable of split- 

 ting up carbon dioxide in the dark and without chlorophyll, so 

 that the above law has lost its universal applicability. This 

 point will be more completely treated in the chapter on the 

 nitrifying bacteria. 



26. Saprophytes and Parasites. 



Plants that are unable to obtain their necessary supplies of 

 material by drawing on the resources of inorganic nature exclu- 

 sively are termed parasites. As is evident from the statements 

 in the preceding paragraph, all the fungi (with some exceptions 

 to be hereafter mentioned) are therefore to be characterised as 

 parasites. Incapable of elaborating the highly complex molecule 

 of their cell substance from the elements or the simplest atomic 

 compounds (C0 2 , H 2 O, NH 3 , &c.), they depend for their supply 

 of nutrient material on ready-formed organic substances, which 

 they have then merely to rearrange according to their needs. 



If this semi-prepared nutriment is obtained from a living 

 creature (animal or plant), such fungi are designated parasitic; 

 but if, on the other hand, they utilise inanimate (or defunct) 

 organic material, they are known as saprophytes. 



