62 



PLANT GROWTH AND NUTRITION 



If the protein is in a liquid state, its presence may be proved 

 by heating, for when it coagulates or thickens, as does the white 

 of an egg when boiled, protein in the form of an albumin is present. 



Another characteristic, protein; test easily made at home is 

 burning the substance. If it burns with the odor of burning feath- 

 ers or leather, then protein forms part of its composition. 1 



A test of the cotyledon of a bean for protean food with nitric 

 acid and ammonium hydrate shows us the presence of this food. 

 Beans are found by actual test to contain about 23 per cent of 

 protein, 59 per cent of carbohydrates, and about 2 per cent oils. 

 The young plant within a pea or bean is thus shown to be well 

 supplied with nourishment until it is able to take care of itself. 

 In this respect it is somewhat like a young animal within the egg, 

 a bird or fish, for example. 



Beans and Peas as Food for Man. So much food is stored in 

 legumes (as beans and peas) that man has come to consider them 

 a very valuable and cheap source of food. Study carefully the 

 following table : 



NUTRIENTS FURNISHED FOR TEN CENTS IN BEANS AND PEAS AT 

 CERTAIN PRICES PER POUND 



1 Other tests somewhat more reliable, but much more delicate, are the biuret 

 test and test with Millon's reagent. 



