Observations upon some Noteworthy Leaf Variations. 291 



of about 1.033 sc l- cm -> tnus standing toward the leaves of the 

 vegetative shoot in the ratio of 1 : 5.45. A recapitulation of 

 these relations is as follows : — 



Spiraea trilobata vanhouttei. 

 Comparative areas of leaves. 



Number 



of 



specimen. 



Number 



of 



leaf on 



specimen. 



Area in 

 sq. cm. 



Average 



area, 

 sq. cm. 



Ratio of 

 areas. 



Flowering 

 branch^ 

 unity. 



Remarks. 



No. 1 



1 

 2 



4.490 



9.650 







Vegetative branch. 





3 



0.440 







Excluded from averages 

 because unusual. 





4 



2.785 



5.640 



1:5.45 





No. 2 



1 



2 



0.290 

 1.995 







Flowering branch. 





3 



0.815 



1.033 



1 :1 







4 



0.685 







Excluded because of 

 unusual size. 





5 



1.805 











6 



3.110 











7 



1.340 



•2.085 



1 :2.70 





In the common basswood (Ti/ia americana) the leaves 

 present variations in form which are confined within such a 

 narrow range as to offer nothing of an exceptional character ; 

 while variations in size are not only of such an exceptional 

 character as to excite comment, but they occur with great 

 frequency and, in this region at least, constitute a well defined 

 feature of the tree under different conditions of growth and in 

 different situations. Individual trees will show a somewhat 

 uniform development of leaves with a diameter of about 8.5 

 cm., and a superficial area of about 55 sq. cm. Other trees — 

 and perhaps more generally — show such leaves in part, to- 

 gether with others about n cm. in diameter and with an area 



