STORAGE OF FOOD IN THE SEED “2A 
a strong magnifying glass, then with a moderate power of 
the compound microscope. To see how dead, dry cell- 
walls, with nothing inside them, look, examine (as before) 
a very thin slice of elder pith, sunflower pith, or pith from 
a dead cornstalk. Look also at the figures in Chapter VI 
of this book. Notice that the simplest plants (Chapter XX) 
consist of a single cell each. The study of the structure 
of plants is the study of the forms which cells and groups 
of cells assume, and the study of plant physiology is the 
study of what cells and cell combinations do. 
* 25. 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 un- 
sprouted cotyledons have disappeared from the shriveled cotyledons 
of the seedlings. A few grains may be left, but they have lost their 
sharpness of outline. 
~26. 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. 
Sometimes the oil is sufficiently abundant to make it 
worth while to extract it by pressure, as is done with flax- 
seed, cotton-seed, the seeds of some plants of the cress 
family, the ‘castor bean,’ and other seeds. 
‘27. Dissolving Oil from Ground Seeds. —It is not possi- 
ble easily 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. 
