24 ELEMENTS OF 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. Experiment 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 dame 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, Fig. 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 
