24 ELEMENTS OE BOTANY. 



33. Oil. — The presence of oil in any considerable quantity 

 in seeds is not as general as is the presence of starch, though 

 in many common seeds there is a good deal of it. 



34. EKperiraent 11.* — To a few ounces of ground flaxseed add 

 an equal volume of ether or benzine. Let it stand ten or fifteen minutes 

 and then filter. Let the liquid stand in a good draught till it has lost the 

 odor of the ether or benzine. 



What have you obtained ? 

 Of what use would it have been to the plant ? 



If the student wishes to do this experiment at home for himself, he 

 should bear in mind the following : 



Caution. — Never handle benzine or ether near a flame or stove. 



35. Albuminous Substances. — Albuminous substances, or 

 proteids, occur in all seeds, though often only in small quanti- 

 ties. They have nearly the same chemical composition as 

 white of egg and the curd of milk among animal substances, 

 and are essential to the plant, since the living and grow- 

 ing parts of all plants contain large quantities of proteid 

 material. 



Sometimes the albuminous constituents of the seed occur 

 in more or less regular grains, Pig. 11. 



But much of the proteid material of seeds is not in any 

 form in which it can be recognized under the microscope. 

 One test for its presence is the peculiar smell which it pro- 

 duces 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 material 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. 



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. Most proteids are turned more or less red 



