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. 
MET ONve TARE (INE, iaPacs <vatersjeie o's «:alelcisnste:Seisicveraremverarere 15 
eC ROLOVCTIAY, =: ..5!c's.c/atuivns fo cic Bal eel epdineue’ canteromeeaes 17 
MAURO O Ue Neeic ss cte:s ste einige uciaie steno wa sate eee 20 
Norm ana enath Of WhEth, TYE, ClC..\..c..2</eccee a ole 15 
SPRSHUMMER DLA Wrsraycta. silos ciaicloseiess.sxes:> a5 a a/e1sislars/ scalars ole eke ae 18 
TEA ia(Ly Cy Ob, KELDEl js... sac.< cs. a.0cie es so eimencieties 14 
PUTA ZC MIGCTMIEL Se 5 5 gabe e:o:d7m%. fejeta's BS aes crepe Lands Sect reeeane 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 free 
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 CeLLtuLosEe Group, or THE AMyLOIDs. 
This group comprises Cellulose, Starch, Inulin, Deatrin, 
Gum, Cane sugar, Fruit sugar, and Grape sugar. 
These bodies, especially cellulose and starch, form by 
far the larger s':are—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, i. e., is made up of minute 
sacks or closed tubes, adhering to each cther. 
