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in the hollows between the angles. The strengthening cells are all thick 
walled and without content. For convenience these cells will be referred 
to as thin and thick walled but the terms are mere relative ones. The 
term strengthening cell, as here used, refers to these thick-walled cells 
wherever found. 
ABIES CONCOLOR. 
D Duets. M Mesophyll. 
B_ Bundle sheath. E Epidermis. 
F Fibro-vas, bundles. S Strength. cells. 
A Strength. cells within sheath. 
