LECTURE V 



THE ROLE OF ELECTROLYTES IN THE FORMATION AND PRES- 

 ERVATION OF LIVING MATTER 



i. ON THE SPECIFIC DIFFERENCE BETWEEN THE NUTRITIVE SOLU- 

 TIONS FOR PLANTS AND ANIMALS 



THE green plants are the factories in which the material for the 

 nutrition for animals and fungi is prepared. The green plant, how- 

 ever, manufactures also, as long as it grows, its own living matter out 

 of the electrolytes of the soil and the CO 2 of the air. The CO 2 is util- 

 ized for the formation of carbohydrates and probably fats; the salts 

 of ammonia, nitrates, phosphates, and sulphates are used for the 

 building lip of nitrogenous compounds. One of the nutritive solutions * 

 which is most commonly used for phanerogamic plants is as follows : 



4 g. Ca(N0 3 ) 2 

 i g. KNO 3 

 i g. MgS0 4 + 7 H 2 

 i g. KH 2 P0 4 

 0.5 g. KC1 



The whole is dissolved in from 3 1. to 7 1. of water. A few drops 

 of ferric chloride are added to this solution. This solution may 

 vary within certain limits. It contains besides the anions CO 3 , NO 3 , 

 SO 4 , and PO 4 , which are necessary for the synthesis of the essential 

 compounds of the plant, the cations K, Ca, Mg, which do not seem 

 equally necessary for the synthesis of living matter. In addition to 

 these, free oxygen is absolutely necessary for the formation of living 

 matter in green plants. 



For the fungi the nutritive solutions are similarly constituted, with 

 this difference only, that they cannot make carbohydrates of CO 2 ; 

 and they are therefore compelled to get their sugar from plants or 

 animals. If raised in a solution containing sugar or certain organic 

 acids (e.g. acetic, tartaric acids) and certain salts, they can also make 



* Knop's Solution. See Pfeffer, PflanzenpJtysiologie, 2d edition, Vol. I, p. 413, 1897. 



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