166 EXPERIMENTS WITH PLANTS 



stance; if the seed-leaf is dry, time must be allowed 

 for the acid to soak into it. Apply the test to a little 

 hard-boiled white of egg. 



Another very excellent test is made by placing on 

 the seed-leaf a drop of a saturated solution of cane- 

 sugar in water; upon this place a drop or two of 

 strong sulphuric acid (chemically pure) ; a bright red 

 color indicates the presence of proteids. 



Which of the three classes of substances seems to 

 be most abundant in the seeds familiar to you I Make 

 a table showing the results of your tests, and indicate 

 by the terms "abundant," "little" or "none,'" the 

 relative quantity found. 



In order that the food materials may reach the 

 places where they are needed, they must travel from 

 cell to cell, passing through the cell -walls. To do this 

 they must be made soluble. The process of making 

 the food soluble is, in a general way, similar in animals 

 and plants: in animals it is called digestion; the pro- 

 cess in animals is better understood than in plants and 

 we may profitably study it in both. In the human body 

 it begins in the mouth, the saliva of which contains a 

 chemical compound called diastase, belonging to the 

 class of bodies known as ferments. In order to observe 

 the action of the diastase, boil a little starch in water 

 to form a paste, and place a little of the cooled paste 

 on the tip of the tongue. After a short time it tastes 

 sweet, indicating that some of the starch has been 



