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by a very regular bundle sheath. In all five species only one fibro-vascular 
bundle is present. Strengthening cells may or may not be present in this 
region, but when present are good determinative features. 
From the data secured from the study of the Picea, the following ar- 
rangement has been made: 
*Ducts always two. 
yLateral axis much longer than dorsi-ventral axis. 
1. Picea Mariana (Mill.) B. 8. P. Strengthening cells in a single row, 
very thick walled, some occur within bundle sheath. 
PICKA CANADENSIS (Alba). 
D Duets. M Mesophyl!. 
S Strength. cells. E Epidermis. 
F Fibro-vas. bundle. B Bundle sheath. 
A Strength.cells within sheath. 
