272 PLANT-LIFE 



this alchemy which is rather bewildering to the human 

 chemist, and it is vital to the existence of the flora and 

 fauna of the whole world. But while our ignorance of 

 the elaborate chemistry of plants is stupendous enough 

 to keep us humble, we are not without some knowledge, 

 which tends to increase, and we need not despair as to 

 the results of present and future research. Setting aside 

 theories and chemical formulae, and all discussion of the 

 method of vegetable chemistry concerning which the 

 doctors may differ, we know that plants elaborate 

 certain products which are easily recognized. First, 

 there are nitrogenous, or nitrogen-containing, products ; 

 these are proteins and albuminoids. The proteins 

 contain carbon, hydrogen, nitrogen, oxygen, and sulphur, 

 and green plants elaborate them from water, carbon 

 dioxide, nitrates, and sulphur compounds. Proteins 

 are essential to the growth of both plants and animals, 

 and the latter are dependent upon the supply manu- 

 factured by the former. Then, secondly, there are non- 

 nitrogenous products, the fats and carbohydrates. The 

 fats contain carbon, hydrogen, and oxygen; they may 

 be derived from carbohydrates or result from the dis- 

 integration of proteins. Fats (or oils) abound in certain 

 seeds, such as linseed, in nuts, and in such fruits as the 

 Olive. Carbohydrates are compounds of carbon, hydro- 

 gen, and oxygen, in which the hydrogen and oxygen 

 occur in the same proportions as in water (HgO) ; they 

 embrace sugar, starch, cellulose, and gum. Starch is 

 an exceedingly important reserve material; it abounds 

 in tubers, such as potatoes, and in starchy seeds — for 

 example, rice, wheat, barley. Starch, being insoluble 

 in water, is transformed into sugar, which is soluble, 



