46 ELEMENTS OE AGRICULTURE, 



when the wood becomes seasoned. Fresh young plants 

 and the leaves of trees contain large amounts of water, 

 75 per cent or more. The trunks of trees and the stems 

 of older plants contain less moisture, usually less than 

 50 per cent. Seeds contain less moisture than any 

 other part of the plant, usually from 10 to 20 per cent. 



41. Dry Matter. — The part of the plant that remains 

 after it is dried is called dry matter, and makes up, 

 as we have seen, from one-tenth to one-fourth of the 

 original weight of young plants. If dried plants are 

 set on fire they burn, and only a little gray powder re- 

 mains. This powder is called ash or mineral matter. 

 When plants are burned, most of the. dry matter disap- 

 pears as smoke and gas, and this part is called the 

 volatile or combustible matter. The amount of 

 dry matter in different parts of the plant depends on 

 the amount of water. The more moisture a plant con- 

 tains the less dry matter, and the less water the more 

 dry matter. 



42. Volatile Matter. — This is the portion of the plant 

 that is changed into gas when the plant is burned, and 

 is often called organic matter. Volatile matter is 

 made up of a number of substances, whicli we may 

 divide into two groups, those containing nitrogen and. 

 those without nitrogen. There are a number of nitro- 

 gen-containing substances in plants, but we shall call 

 them all by one name, protein. There are also a great 

 many substances in the plant which contain no nitrogen, 

 and those we shall call non-nitrogenous. The 

 amounts of protein and non-nitrogenous substances 

 vary in different plants, and in different parts of the 



