62 



PLANT GROWTH AND NUTRITION 



If the protein is in a liquid state, its presence may be proT^ed 

 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.^ 



A test of the cotyledon of a bean for protein 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 



Food Materials as Purchased 



Kidney beans, dried 



Lima beans, fresh, shelled . . . 



Lima beans, dried 



String beans, fresh, 30 cents per 



peck 



Beans, baked, canned . . . . 



Lentils, dried 



Peas, green, in pod, 30 cents per 



peck 



Peas, dried 



Prices 



PER 



Pound 



Cents 



5 



8 

 6 



3 



5 



10 



3 

 4 



Ten Cents will pay- fob — 



Total 



Food 



Material 



Pounds 



2.00 

 1.25 

 1.67 



3.33 

 2.00 

 1.00 



3.33 

 2.50 



Proteid 



Pounds 



0.45 

 .04 

 .30 



.07 

 .14 

 .26 



.12 

 .62 



Fat 



Pounds 



0.04 



.03 



.01 

 .05 

 .01 



.01 

 .03 



Carbo- 

 hydrates 



Pounds 



1.19 



.12 



1.10 



.23 

 .39 

 .59 



.33 

 1.55 



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

 test and test with Millon's reagent. 



