THE VOLATILE PAET OP PLANTS. 39 



Oxygen 88.89 



Hydrogen 11.11 



100.00 



It exists in all parts of plants, is the immediate cause 

 of the succulence of their tender portions, and is essen- 

 tial to the life of the yegetable organs. 



In the following table are given the percentages of water in some of 

 the more common agricultural products in the fresh state, but the pro- 

 portions are not quite constant, even in the same part of different 

 specimens of any given plant. 



WATEK IN FKESH PLANTS. (PER CENT.) 



Average. Range. 



Meadow grass 71 60 to 78 



Eedolover 80 68 " 86 



Maize, as used for fodder 82 71 " 93 



Cabbage 85 80 "94, 



Potatotubers 75 77 "82 



Sugarbeets 81 76 "90 



Carrots 86 79 "90 



Turnips 91 86 "93 



■In living plants, water is usually perceptible to the 

 eye or feel, as sap. But it is not only fresh plants that 

 contain water. When grass is made into hay, the water 

 is by no means all dried out, but a considerable propor- 

 tion remains in the pores, which is not recognizable by 

 the senses. So, too, seasoned wood, flour, and starch, 

 when seemingly dry, contain a quantity of invisible 

 water, which can be removed by heat. 



Exp. 21.— Into a wide glass tube, like that shown in Pig. 2, place a 

 spoonful of saw dust, or starch, or a little hay. Warm over a lamp, 

 but very slowly and cautiously, so as not to burn or blacken the sub- 

 stance. Water will be expelled from the organic matter, and will col- 

 lect on the cold part of the tube. 



It is thus obvious that vegetable substances may eon- 

 tain water in at least two different conditions. Eed 



clover, for example, when growing or ^ ^-^ 



freshly out, contains about 80 per cent of 

 water. When the clover is dried, as for __ 



making hay, the greater share of this wa- '' / I 

 ter escapes, so that the air-dry plant con- 

 tains but about 15 per cent. On subject- "^ 

 ing the air-dry clover to. a temperature '^' ' 

 at 312 ° for some hours, the water is completely expelled, 

 and the substance becomes really dry, i. e., water-free. 



