14 HOW CROPS GRO\V. 



Organic matters are in general characterized by com- 

 plexity of constitution, and are exceedingly numerous 

 and various ; while inorganic bodies are of simpler com- 

 position, and comparatively few in number. 



VOLATILE AND FIXED MATTER. All plants and ani- 

 mals, taken as a whole, and all of their organs, consist of 

 a volatile and fixed part, which may be separated by 

 burning ; the former usually by far the larger share 

 passing into and mingling with the air as invisible gases ; 

 the latter forming, in general, but from one to five per 

 cent, of the whole remaining as ashes. 



EXPERIMENT 1. A splinter of wood heated in the flame of a lamp 

 takes fire, burns, and yields i-nlntih- nnitti-r. which consumes with flame, 

 and ashes, which are the only visible residue of the combustion. 



Many organic bodies, products of life, but not essential 

 vital organs, as sugar, citric acid, etc., are completely 

 volatile when in a state of purity, and leave no ash. 



USE OF THE TERMS ORGANIC AND INORGANIC. -It is 

 usual among agricultural writers to confine the term or- 

 ganic to the volatile or destructible portion of vegetable 

 and animal bodies, and to designate their ash-ingredients 

 as inorganic matter. This is not an entirely accurate 

 distinction. What is found in the ashes of a tree or of a 

 seed, in so far as it was an essential part of the organism, 

 was as truly organic as the volatile portion, and, by sub- 

 mitting organic bodies to fire, they may be entirely con- 

 verted into inorganic matter, the volatile as well as the 

 fixed parts. 



ULTIMATE ELEMENTS THAT CONSTITUTE THE PLANT. 

 Chemistry has demonstrated that the volatile and de- 

 structible part of organic bodies is chiefly made up of four 

 substances, viz. : carbon, oxygen, hydrogen, and nitrogen, 

 and contains two other elements in lesser quantity, viz. : 

 sulphur and phosphorus. In the ash we may find phos- 

 phorus, sulphur, silicon, chlorine, potassium, sodium, cal- 



