STORAGE OF FOOD IN THE SEED 23 



form in which it can be recognized under the microscope. 

 One test for its presence is the peculiar smell which it 

 produces in burning. Hair, wool, feathers, leather, and 

 lean meat all produce a well-known sickening smell when 

 scorched or burned, and the similarity of the proteid mate- 

 rial in such seeds as the bean and pea to these substances 

 is shown by the fact that scorching beans and similar 

 seeds give off the familiar smell of burnt feathers. 



29. Chemical Tests for Proteids. All proteids (and 

 very few other substances) are turned yellow by nitric 

 acid, and this yellow color becomes deeper or even orange 

 when the yellowish substance is moistened with ammonia. 

 They are also turned yellow by iodine solution. Most 

 proteids are turned more or less red by the solution of 

 nitrate of mercury known as Millon's reagent. 1 



EXPERIMENT X 



Detection of Proteids in Seeds. Extract the germs from some 

 soaked kernels of corn and bruise them; soak some wheat-germ meal 

 for a few hours in warm water, or wash the starch out of wheat- 

 flour dough ; reserving the latter for use, place it in a white saucer or 

 porcelain evaporating dish, and moisten well with Millon's reagent 

 or with nitric acid ; examine after fifteen minutes. 



30. The Brazil-Nut as a Typical Oily Seed. Not many 

 familiar seeds are as oily as the Brazil-nut. Its large size 

 makes it convenient for examination, and the fact that this 

 nut is good for human food makes it the more interesting 

 to investigate the kinds of plant-food which it contains. 



i See Handbook. 



