176 VEGETABLE PHYSIOLOGY 



CHAPTEK XII 



THE CONSTITUENTS OF THE ASH OF PLANTS 



We have seen in a previous chapter that when a plant is 

 carefully burned and the residue collected, the latter, which 

 is known as the ash, is found to contain a number of elements 

 which vary in different cases and which always include 

 certain metals, as well as some non-metallic elements. The 

 occurrence of this ash being universal, we can conclude 

 without any difficulty that some of its constituents at least 

 must be of importance to the organism, though it cannot 

 be denied that our information is exceedingly incomplete. 

 It is certainly possible, if not actually probable, that a 

 definite association of any of the elements with a particular 

 function does not and cannot exist. Even in the animal 

 body, the study of which is far more complete than that 

 of the plant, such association has not been found. Each 

 element plays more than one part, and not improbably the 

 role it plays at any moment depends to a very large extent 

 on the condition of the organism. We may well conclude 

 that in the organisation of the plant also there is no definite 

 devolution of a particular function to a single constituent 

 of its composition. It is probable that the well-being of 

 any organism depends on the interaction of many elements 

 with the protoplasm interaction which may vary from 

 time to time and from place to place, according to the 

 changes of the environment or the automatic readjustments 

 going on in the living substance. The influence of varying 

 quantities of the mixture of elements may be considerable. 

 Correlations of the functions of the plant, or the abnormal 



