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DEPARTMENT OF AGRICULTURE GEORGIA. 



[344] 



In speaking of the chemical composition of plants, the 

 ultimate constituents or elements will be seldom mentioned, 

 since they are never taken up by plants in their elementa- 

 ry forms, but as proximate principles, or compounds. 



To illustrate : Carbon is taken into the plant in the form 

 carbonic acid gas ; phosphorus, as phosphoric acid ; nitro- 

 gen, as ammonia, nitric acid, etc. 



The proximate organic principles are divided into "carbo- 

 hydrates, albuminoids, vegetable acids, vegetable oils, al- 

 kaloids, and coloring matters." 



Carbo-hydrates, so named from being composed of carbon 

 hydrogen and oxygen, are subdivided into woody fibre, 

 starch, sugar, gums, and jellies, all of which are objects 

 of interest to a greater or less extent to the agriculturist. 



Cellulose, the principal constituent of woody fibre, forms 

 a very large part of all vegetable structure, serving as the 

 framework of the organism, and especially of the cell 

 walls. 



4 'Cellulose exists in various vegetable matters, when air- 

 dried, in the following proportion : 



Per cent. Per cent. 

 Potato tuber 1.1 Clover hay 34.0 



Wheat kernel 3.0 



Maize kernel.. .. 3.5 



Barley kernel 8.0 



Oat straw.., ..10.3 



Maize cobs 38.0 



Oat straw 40.0 



Wheat straw 48.0 



Rye straw 54.0 



Scientific Agriculture. Pendleton. 



Lignin is more dense, contains more carbon, and is less 

 digestible than the cellulose. 



Starch is very abundant in many vegetables, and espe- 

 cially so in many seeds and tubers. It is found within the 

 cell-walls in very minute grains. It is made from various 

 grains and tubers, by first grating, grinding, or otherwise 

 pulverizing the substance, so as to break the cell-walls, 

 when the powder or flower is washed with water, the starch 

 grains held in suspension allowed to settle, the water 

 poured off, and the deposited starch dried. Or, the albu* 



