54 HOW CROPS GROW. 



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

 mens of any given plant. 



WATER (per cent) IN FRESH PLANTS. 



Meadow grass 72 



Red clover. 79 



Maize, as used for fodder 81 



Cabbage 90 



Potato tubers 75 



Sugar beets 82 



Carrots 85 



Turnips 91 



Pine wood 40 



In living plants, water is usually perceptible to the eye 

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

 tain water. When grass is made into hay, the water is by 

 no means all dried out, but a considerable proportion re- 

 mains 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 fig. 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 substance. 

 Water will be expelled from the organic matter, and will collect on the 

 cold part of the tube. 



It is thus obvious that vegetable substances may con- 

 tain water in two different conditions. Red clover, for 

 example, when growing or freshly cut, 

 contains about 79 per cent of water. 

 When the clover is dried, as for making 

 hay, the greater share of this water es- 

 capes, so that the air-dry plant contains 

 but about 17 per cent. On subjecting the 

 air-dry clover to a temperature of 212 

 for some hours, the water is completely expelled, and the 

 substance becomes really dry. 



To drive off all water from vegetable matters, the chemist usually em- 

 ploys a water-bath, fig. 9, consisting of a vessel of tin or copper plate, 

 with double walls, between which is a space that may be nearly filled 

 with water. The substance to be dried is placed in the iuterior chamber, 



