CONDITIONS OF LIFE OF THE MOULD FUNGI. 507 



probably contained in all true albuminous materials. 

 According to Nageli's experiments, it can be taken from 

 the albuminates, and as well, or better, from sulphates, 

 sulphites, or hyposulphites ; sulpho-acids may also act 

 as substitutes, but not sulpho-urea compounds or the 

 sulpho-cyanides. Exact experiments, however, as to 

 the supply of sulphur are very difficult to carry out, 

 because the small quantities necessary for suitable 

 nourishment commonly adhere as impurities to the 

 other nutrient materials, as for example, to the sugar. 



Water and mineral substances are of great importance Supply of 

 for the nourishment of the mould fungi. A large ^ 

 quantity of water is necessary for the nutriment of the 

 mould fungi; in part it enters into the complex sub- 

 stances which are built up by the fungi, in part it forms 

 the chief constituent of the newly formed tissue of the 

 fungus, and in part it acts as a dissolving and trans- 

 porting medium, and thus enables the materials to 

 move in the cell, just as in the case of the higher 

 organisms. It is of special interest, as regards the 

 necessity for water, to ascertain the smallest quantity 

 necessary for the mould fungi to obtain sufficient 

 nourishment. As regards this question we shall enter 

 into further details when considering the subject of 

 nutrient materials with reference to their concentra- 

 tion. According to Nageli's more recent researches, Need of 

 a relatively small quantity of mineral substances are 

 necessary. While the chlorophyllous plants require, 

 besides phosphoric acid, sulphuric acid, and alkalies, 

 also calcium and magnesium, and in addition iron, 

 silicic acid, and chlorine, the mould fungi are satisfied 

 with sulphuric acid, phosphoric acid, potash, and calcium 

 or magnesia. The potash, however, cannot be replaced 

 by sodium, although it may by caesium and rubidium. 

 In the place of calcium we may have, besides magnesium, 

 also barium or strontium. One element from the group 

 of the alkalies, and one from the alkaline earths, must, 

 however, always be present ; each of these representa- 

 tives of the two groups appear to have different functions, 

 which are probably the following : the earthy com- 



