CHAPTER XIV. 



ROUGH ANALYSIS OF PLANT SUBSTANCE. 



148. Some simple experiments to indicate the nature of 

 plant substance. — After these building-up processes of the plant, 

 it is instructive to perform some simple experiments which indi- 

 cate roughly the nature of the plant substance, and serve to 

 • show how it can be separated into other substances, some of them 

 being reduced to the form in which they existed when the plant 

 took them as food. For exact experiments and results it would 

 be necessary to make chemical analyses. 



Exercise 30. 



149. The water in tlie plant. — Take fresh leaves or leafy shoots or other 

 fresh plant parts. Weigh. Permit them to remain in a dry room until they 

 are what we call "dry." Now weigh. The plants have lost weight, and 

 from what we have learned in studies of transpiration this loss in weight we 

 know to result from the loss of water from the plant. 



Exercise 31. 



150. The dry plant material contains water. — Take dry leaves, shavings, 

 or other dry parts of plants. Place them in a test-tube. With a holder rest 

 the tube in a nearly horizontal position, with the bottom of the tube in the flame 

 of a bunsen burner. Very soon, before the plant parts begin to "burn," 

 note that moisture is accumulating on the inner surface of the test-tube. 

 This is water driven cff which could not escape by drying in air, without the 

 addition of artificial heat, and is called " hygroscopic water." 



151. Water formed on burning the dry plant material. — Light a soft-pine 

 or bass-wood splinter. Hold a thistle tube in one hand with the bulb down- 

 ward and above the flame of the splinter. Carbon will be deposited over the 

 inner surface of the bulb. After a time hold the tube toward the window 

 and look through it above the carbon. Drops of water have accumulated on 



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