232 Eei'oht ox Crop Pkoduction of the 



CHEMICAL ELEMENTS IN PLANTS. 

 One of the qiiestionis wliich early engaged the attentionl of 

 chemists 'and plant physiologists was the determination of the 

 number and function of the elements necessary for the growth 

 of plants. Numerous investigations, few of which have 'been 

 conducted within recent years, have, witbout question, justified 

 the conclusion that at least eleven elements are essentially' in- 

 volved in the normal development of agricultural plants. 

 Whether or not certain others, ordinarily found in vegetable 

 ti£isue, are requisite to the functions of plant life, or at least to 

 its well being, is a question which so far does not appear to have 

 been definitely settled. Moreover, concerning the necessary pro- 

 portions of the mineral ingredients of plants no satisfactory con- 

 clusionis seem to have been reached. It does not jet appear, 

 for instance, that, because wheat takes up sodium, this species 

 of grain must have this element in order to attain full develop- 

 ment, or that when a certain quantity of potassium is found in 

 a particular wheat crop, less of this element might not have met 

 all requirements. Our present state of knowledge allows us to 

 infer that a plant in appropriating raw materials for construc- 

 tive purposes may exercise a selective power not strictly in ac- 

 cordance with its exact needs. It may possibly absorb materials 

 unnecessary either in the kind or in the quantity used. Notwith- 

 standing all this, it is clearly established that all the elements 

 of the organic part of a plant are absolutely essential to growth 

 and that in the absence of some of those found in the ash, growth, 

 if it takes place at all, goes on abnormally. 



POTASH AND SODA. 



Since the earliest investigations of thirty years ago or more 

 it has been taught that agricultural plants cannot attain normal 

 development in the absence of potash. Concerning the essential- 

 ness of soda to plant life, more or less doubt still exists. It is 

 generally believed by agricultural chemists that if it is necessary 

 at all, only minute quantities are needed. While these views 



