SECTION I.— PLANT LIFE 



CHAPTER I 

 The Ultimate Constituents of Plants 



The ultimate constituents of plants may be defined as the actual 

 chemical elements existing in plants, as distinct from the chemical 

 compounds of which those elements are the component parts. 



Of all the seventy odd elements at present known, only twelve 

 or so occur in plants in sufficient amounts to be of importance, and 

 of these twelve elements, three — namely, nitrogen, phosphorus, 

 and potassium — are generally regarded as of especial chemical 

 significance. 



The ash of plants contains the non-volatile bodies left after 

 ignition, and consists largely of the carbonates and phosphates of 

 calcium and potassium, although these salts need not have been 

 present as such in the living plant. A knowledge of the elements 

 present in the ash is of importance, as these constituents are all 

 obtained by the plant from the soil. 



The water or moisture present in plants should not strictly be 

 considered under the head of ultimate constituents. 



1. Qualitative Detection of Nitrogen. 



(a) A gram or so of the substance under observation 

 is well mixed with two to three times its weight of soda- 

 lime and heated to redness in a hard-glass tube. The 

 nitrogenous compounds present are converted into 

 ammonia, the presence of which may be detected at 

 the mouth of the tube by its smell and by its action 

 on litmus. (Will and Varrentrap.) 



(J?) A small quantity of the substance is placed in 



