SAPROPHYTES AND PARASITKS 23 



Owing- to their greater size, and consequent discernibility, the algie formed 

 the subject of investigation at a much earlier date than the very much smaller 

 fission fungi, which necessitated the employment of more perfect methods of 

 examination, so that, by the time the latter began to be studied, the green algae 

 had already been systematised. The temptation to include the newly-discovered 

 bacteria among the analogous algre was therefore great, and thus it was that the 

 meritorious German algologist FR. KUTZING (I.) was induced to ascribe the 

 acetic acid ferment discovered by him, and now known as Jlacterium aceti, to the 

 algai, under the name of Ulvina aceli. 



This inclination to regard fission fungi and alga; ;is belonging to the same 

 class was also manifested by subsequent workers, and the more so since the 

 greater insight gained in the interim spoke more conclusively in its favour than 

 was possible in the initial, imperfect stage of knowledge. Hence FERDINAND 

 COHN (II.) in 1875 was obliged to discard his own (IV.) term for the bacteria, 

 viz., Schizosporce, as also that (Schizomycetes) proposed by Nageli (V.) in 1857, 

 and to classify these organisms with the lowest of the alga3 (Nostoc, Ohroococcus, 

 Merismopedia, Oscittaria, <fec.) into one group, which, from their common and 

 characteristic property of reproduction by fission, he called Schizophytce (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 

 Algca and Fungi, 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 pare 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 9 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 tho assistance of light and 

 chlorophyll, and as the fungi are, without exception, devoid of the last-named 

 substance, it has been laid clown as a law that the fungi are incapable of 

 assimilating carbon dioxide and of constructing their cells of inorganic substances 

 like the algre.do. The researches of Winogradsky have, however, shown that 

 there are fission fungi capable of splitting 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 exclusively 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 9 , 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 



