THE VOLATILE PART OF PLANTS. 55 
the door is closed, and the water is brought to boil by the heat of a lamp 
or stove. The precise quantity of water belonging to, or contained in, a 
substance, is ascertained by first weighing the substance, then drying it 
until its weight is constant. The loss is water. 
In the subjoined table are given the average quantities, per cent, of 
water existing in various vegetable products when air-dry. 
WATER IN AIR-DRY PLANTS. 
Meadow grass, (MOy,).....0.0 ccc cece ee en cee eeceneee 15 
Redielover hays ¢viscis.s sisdsie-s escieiad sinceioie s saibss positive sieece 17 
Pine? W00 Geass ere-osiereig organs g eeu tesaaites Sega Peas Sree 20 : 
Straw and chaff of wheat, rye, cte..... 2... eee eee ee 15 
Bean StraWieey's sacise eee ss sees rahe grargeaho SNS eS w slate -ers ines 18 
Wheat, (rye, oat,) kernel... ........-ce cece essences 14 
Maize ern el ocisicstecsce-eisinisig. 0 vi ses areaters scetciers 9 sidiesei avers 12 
That portion of the water which the fresh plant loses by 
mere exposure to the air is chiefly the water of its juices 
or sap, and is manifest to the sight and feel as a liquid, in 
crushing the fresh plant; it is, properly speaking, the jree 
water of vegetation. ‘The water which remains in the air- 
dry plant is imperceptible to the senses while in the plant, 
—can only be discovered on expelling it by heat or other- 
wise,—and may be designated as the hygroscopic water of 
vegetation. , 
The amount of water contained in either fresh or air- 
dry vegetable matter is constantly fluctuating with the 
temperature and the dryness of the atmosphere. 
2. Tur CEeLLuLose Group, on THE AMYLOIDS. 
This group comprises Cellulose, Starch, Inulin, Dextrin, 
Gum, Cane sugar, Fruit sugar, and Grape sugar. 
These bodies, especially cellulose and starch, form by 
far the larger share—perhaps seven-eighths—of all the dry 
matter of vegetation, and most of them are distributed 
throughout all parts of plants. 
Cellulose, C,, H,, O,,—Every agricultural plant is an 
aggregate of microscopic cells, 1. e., is made up of minute 
sacks or closed tubes, adhering to each other. 
