STORAGE OF FOOD IN THE SEED 17 
the same relation to the plant of which it is a part that 
one cell of a honeycomb does to the whole comb. Cells 
are of all shapes and sizes, from little spheres a ten-thou- 
sandth of an inch or less in diameter to slender tubes, 
such as fibers of cotton, several inches long. To get an 
idea of the appearance of some rather large cells, scrape a 
little pulp from a ripe, mealy apple, and examine it first 
Fie. 8. ‘Section through Exterior Part of a Grain of Wheat. 
c, cuticle or outer layer of bran; ep, epidermis; m, layer beneath epider- 
mis; gu, sch, layers of hull next to seed-coats; br, n, seed-coats; Al, 
layer containing proteid grains; st, cells of the endosperm filled with 
starch. (Greatly magnified.) 
with 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 VII of this book. Notice that the simplest plants 
(Chapter XXIII) consist of a single cell each. The study 
