120 
boretum, and comprised only truly American species. The collection con- 
sisted of six species of Abies and five of Picea, all of the United’ States. 
In preparing the leaves for study, transverse sections were made 
through the center of the leaf so as to avoid the danger of getting sections 
without the characteristic number of ducts or fibro-vascular bundles. AI- 
ABIES GRANDIS. 
D Duets. M Mesophyll. 
B Bundle sheath. E Epidermis. 
F Fibro-vas. bundle. S Strength. cells. 
together, between five and six hundred specimens were studied. In this 
determination only features represented in these transverse sections were 
used. 
In the genus Abies the leaf structure is essentially the same as that 
of the genus Pinus. The leaf, as a whole, is divided into three parts, the 
