CONDITIONS OF LIFE OF THE MOULD FUNGI. 505 



hydrochlorate of methylamine and aethylamine, tri- 

 methylamine ; leucine, asparagine; acetamide, oxamide ; 

 and urea. The best nitrogenous nutrient materials 

 were the soluble albuminates and peptone. Nitrogen 

 can also be assimilated by the mould fungi from 

 nitrates; probably in this case there is a gradual 

 reduction of the nitric acid to nitrous acid, and ulti- 

 mately to ammonia ; but these reduction products have 

 not yet been demonstrated. In comparative experi- 

 ments no marked difference was found between the 

 nutrient value of the nitrates and the salts of ammonia ; 

 urea was better than either, and peptone was better 

 than urea. 



The necessary carbon can be obtained from the For the supply 

 groups CH 3 or CH 2 , and in that case it is of advantage, of carbon ' 

 and under certain circumstances necessary, that several 

 carbon atoms should be united in one molecule. No 

 carbon can be assimilated if in any given chemical com- 

 bination there is only a union of carbon with nitrogen, 

 oxygen, or carbon. Hence the following substances are 

 not suitable for yielding carbon : carbonic acid, cyanogen, 

 formic acid, urea, oxalic acid, and oxamide. Of course, 

 also, those combinations which are not soluble in water 

 are unsuitable as food, such as the higher fatty acids 

 and the insoluble humine substances. Apart from the 

 number of the carbon atoms, the ease with which the 

 compounds can be decomposed seems to be of import- 

 ance ; the more readily the compound can be broken up 

 by other agents, such as by oxidising substances, the 

 more easily can it be assimilated. Nageli has formed 

 the following empirical table of the nutrient value of 

 various organic compounds with regard to carbon : 1. 

 Various kinds of sugar. 2. Mannite, glycerine ; the 

 carbon group in leucine. 3. Tartaric acid ; citric acid ; 

 succinic acid ; the carbon group in asparagine. 4. Acetic 

 acid ; sethylic alcohol ; quinic acid. 5. Benzoic acid ; 

 salicylic acid ; the carbon group in propylamine. 6. 

 The carbon group in methylamine ; phenol. Pyrogallic 

 acid and tannic acid were also fairly good sources of 

 carbon ; and finally we may mention the observa- 



