FUNGI : CHEMICAL CONSTITUENTS. 179 



40 to 80 per cent. The moulds and the vegetative parts of 

 higher fungi contain from 80 to 90 per cent., whilst in the 

 resting and reproductive organs the percentage is much 

 lower. 



In common with all organised bodies, the fundamental 

 chemical constituents of fungi are the elements carbon, 

 hydrogen, oxygen, and nitrogen. The relative amount of 

 ash is found to vary enormously ; the mycelia of Aspergillus 

 and Penicillium contain about 6 per cent, of ash. The mineral 

 substances which may be regarded as essential constituents 

 of fungi are sulphur, phosphorus, chlorine, potassium, calcium, 

 magnesium, iron, manganese, and sodium. Sulphur and 

 phosphorus are of special importance, as they form necessary 

 components of the albuminoids. Some idea of the importance 

 of the phosphorus present may be gathered from the fact 

 that its proportion in the ash may often amount to half the 

 total quantity. Chlorine, which apparently plays an important 

 part in the nutrition of fungi, and which may be concerned in 

 bringing about the dissociation of the nutrient fluids, probably 

 occurs in all fungi. 



Amongst the metals, potassium occurs in the largest 

 proportion, whilst calcium and magnesium are present in 

 smaller amounts. The same is true of iron and manganese, 

 which, although occurring in comparatively small propor- 

 tions, are nevertheless of the highest importance to the 

 organism in the different phases of its life history. 



Cellulose, the carbohydrate which is of such general 

 occurrence amongst the higher plants, is found also in the 

 walls of fungus cells, but the mucilaginous or viscous sub- 

 stances which often characterise the cell-walls of the former 

 occur comparatively seldom. Yeast mucilage is, however, a 

 well-known example of this. Foremost among the substances 

 forming the contents of fungus cells must be mentioned the 

 proteins or albuminoids, which are in all probability the 

 actual carriers of the vital phenomena. They possess in addi- 

 tion a practical significance ; yeast, for example, which is 

 very rich in albuminoids may be used for the preparation of 

 nutritive media to take the place of meat-broth, etc. 



The nucleins may be regarded as constituting a special 



