18 ESSENTIALS OF BOTANY 
of the structure of plants is the study of the forms which 
cells and groups of cells assume, and the study of plant physi- 
ology is the study of what cells and cell combinations do. 
21. Absorption of Starch from the Cotyledons.— Examine with 
the microscope, using a medium power, soaked beans and the cotyle- 
dons from seedlings that have been growing for three or four weeks, 
Stain the sections with iodine solution, and notice how completely 
the clusters of starch grains that filled most of the cells of the 
unsprouted cotyledons have disappeared from the shriveled cotyle- 
dons of the seedlings. A few grains may be left, but they have lost 
their sharpness of outline. 
22. Oil. — The presence of oil in any considerable quan- 
tity in seeds is not as general as is the presence of starch, 
though in many common seeds there is a good deal of it. 
Sometimes the oil is sufficiently abundant to make it 
worth while to extract it by pressure, as is done with 
flaxseed, cotton-seed, the seeds of some plants of the cress 
family, the “castor bean” and other seeds. 
23. Dissolving Oil from Ground Seeds. — It is not easily 
possible to show a class how oil is extracted from seeds 
by pressure ; but there are several liquids which readily 
dissolve oils and yet have no effect on starch and most 
of the other constituents of seeds. 
EXPERIMENT VI. 
Extraction of Oil by Ether or Benzine. — 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 saucer 
or evaporating dish in a good draught till it has lost the odor of the 
ether or benzine. 
Describe the oil which you have obtained. 
