552 VITAL ACTIONS OF THE LOWER FUNGI. 



ments showed an equally marked multiplication of the 

 organisms if the growth was allowed in the first place to 

 attain its maximum, and if the water was then sterilised 

 and again sown with individuals of the same species of 

 bacteria; this occurred on several repetitions of the 

 process. In this case it is evident that the products of 

 tissue change must have been to a great extent excreted 

 in a form which could again be utilised, and that the 

 dead individuals could in like manner serve as nutrient 

 material. It is only by some supposition of this kind 

 that we can conceive the continuation of the life of these 

 fungi with such a slight diminution of the organic 

 materials, and the repeated development of new genera- 

 tions on the same substrata. 

 Non-nitrogen- Non-nitrogenous plastic materials seem to play a 

 much less important part in the life of the fungi than 

 in that of the higher plants. Starch is only found in 

 exceptional cases, and of the other carbo-hydrates we 

 find, in the case of mould fungi, trehalose and glucose, 

 and in some cases also the alcohol mannite, which is 

 usually reckoned among the carbo-hydrates. Of organic 

 acids, tartaric acid, malic acid, and citric acid are usually 

 reckoned as plastic materials, but as regards their destiny 

 in the fungi nothing is as yet known ; fatty oil seems, 

 however, to be a frequent constituent of the cells of 

 the fungi. Along with these mobile matters, corre- 

 sponding in so far to soluble albumen, we have also 

 cellulose, which is deposited in the cells and constitutes 

 in the case of the mould and yeast fungi almost the 

 whole of the cell membrane, but in the fission fungi 

 only a small portion (see p. 526). These materials 

 are taken up from the nutrient substrata only to a 

 slight extent in a prepared and utilisable form. As a 

 rule, they arise in two ways, which very probably are 

 often combined. We either find that they are built up 

 of more simple compounds, as is, for example, certainly 

 the case when relatively simple compounds (acetic acid, 

 alcohol, leucine) are the sole source of carbon, or the 

 non-nitrogenous plastic materials arise by the splitting 

 up of more complex molecules, and more especially of 



