THE FOOD OF PLANTS. 1 25 



number of plants in artificial soils containing salts of these acids, and 

 prevented any access of carbon dioxide to the leaves. He found, on the 

 whole, that the plants gained in dry weight, and he concluded that these 

 acids can supply carbon to the plant. Schmoeger, however, in repeating 

 the experiments, found that these salts undergo decomposition in the soil, 

 carbon dioxide being evolved, and he attributes the increase of weight 

 observed by Stutzer to the absorption by the leaves of the plants of the 

 carbon dioxide evolved from the salts of the soil during the experiment. 



Plants which do not contain chlorophyll, and which must therefore 

 take up their carbon in the form of complex compounds, are either 

 parasites, that is they live upon other living organisms, or saprophytes, 

 that is they live upon the products of the waste and decay of other living 

 organisms. The plants which do not contain chlorophyll are the Fungi, and 

 a few Phanerogams, Epipogium Gmelini, Cuscuta, Monotropa, Lathraea, 

 Corallorhiza ; of these the Fungi include both parasites and saprophytes, 

 Epipogium Gmelini is a saprophyte, Cuscuta a parasite, and Monotropa, 

 according to Drude, may be either the one or the other. The Orobancheas, 

 which are parasitic, and Neottia, which is saprophytic, have not a green 

 colour, but nevertheless small quantities of chlorophyll have been detected 

 in them. 



Although the Fungi cannot assimilate carbon in the form of carbon 

 dioxide, yet they can assimilate it in compounds which cannot be assimi- 

 lated by green plants. This subject has been investigated by Naegeli, 

 and the following is a list of the organic substances, arranged in order 

 according to their nutritive value, which he found to be assimilated by 

 various Fungi (Yeast, Bacteria, Moulds). 



1. The different kinds of sugar. 



2. Mannite : Glycerin : the carbon-group in Leucin. 



3. Tartaric acid : Citric acid : Succinic acid : the carbon-group "in 

 Asparagin. 



4. Acetic acid : Ethyl-alcohol : Quinic acid. 



5. Benzoic acid : Salicylic acid : the carbon-group in Propylamine. 



6. The carbon-group in Methylamine : Phenol. 



He found that they could not assimilate carbon in the form of cyanogen- 

 compounds, of urea, of formic acid, and of oxalic acid. The acids men- 

 tioned above were in combination with ammonia. 



The carbon absorbed in any of these forms is used 

 within the plant for the formation of substances which either 

 take part in the building up of the plant, or undergo decom- 

 position, energy being thereby set free in the plant. The 

 processes by which these combinations and decompositions 

 are effected will be fully considered hereafter. 



Hydrogen. This element is absorbed by all plants alike 



