286 Canadian Record of Science. 



within ioo feet, it was evidently crowded by the shrubs on 

 each side, and these at any rate established conditions of 

 relative shade by reason of their greater height of three to four 

 feet. 



In the case of the first short shrub which I have desig- 

 nated as number four, and which is represented by figure 5, 

 this plant was situated on the easterly side of the clump, and 

 it therefore received the sun only in the early part of the 

 morning, being shaded during the greater part of the day. 

 While this shrub showed about 30 to 40 % of leaves similiar 

 to those of number three (Fig. 4), the majority were strictly 

 dorsi-ventral on plagiotropic branches, and they approximated 

 to the normal type not only in position, but in form and size 

 (Fig. 4, 1-8 in acropetal succession, one of each pair of leaves 

 from the same branch). Here it will be seen that there is 

 marked variation from an orbicular to an oblong-lanceolate 

 leaf, with corresponding differences in size — the largest, (2, 

 3, 4,) approaching most nearly to the typical leaf, especially 

 with respect to the form of the base. The apex of these 

 leaves is more variable than in other cases, varying from acute 

 to obtuse and mucronate, to retuse. These leaves, which 

 most nearly approach what Gray holds to be the typical form, 

 range in superficial area, from 3.85 sq. cm., to 28.85 S T cm -> 

 with an average of about 13.54 sq. cm. In specimen number 

 1 (Fig. 2), the leaves from 1-7 represent single members of 

 each pair in acropetal succession, taken from the same branch, 

 This branch was selected because it represented the average 

 character of the prevalent form and size of leaf. It will be 

 noted that although the apex varies somewhat, there is great 

 constancy in the form of the base and the general outline, 

 and not more variation in size than is commonly met with in 

 trees and shrubs generally. These leaves range from 13.00 

 sq. cm. to 28.33 sq. cm., with an average of area of about 

 18.28 sq. cm. To recapitulate these dimensions for all our 

 specimens, the following tabulation will be of interest : — 



