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The fibro-vascular region lies in the center of the leaf and is surrounded 
by a somewhat imperfect bundle sheath. The sheath is composed of large 
and small cells intermingled. In the center lie the fibro-vascular bundles, 
which are two in number, with the exception of Abies magnifica, where 
the two seem to have merged into one. Strengthening cells sometimes 
appear within the bundle sheath and seem to be a constant feature in the 
species in which they occur. ; 
PICEA RUBRA, 
D Duets. E Epidermis. 
S Strength. cells. M Mesophgll. 
F Fibro-vas. bundle. B Bundle sheath. 
A Strength. cells within sheath. 
