Senile Changes in Leaves of Certain Plants 323 



TABLE 36. Relation of Size of Vein Islets to Age in Tilia Americana L. 



Diameter of trunk (in centimeters) 



7.6 



35.7 



Area of leaf (in square centimeters) 



30.0 

 0.04 



1,560 



Area of islets (in square millimeters) 



02 







In the latter case the leaves were borne by water sprouts growing from the stump and they 

 were fifty times the size of the leaves on the small tree; yet the size of the vein islets cor- 

 responded to the age of the plant. 



TABLE 37. Relation of Size of Vein Islets to Age in Ulmus Americana L. 



Diameter of trunk (in centimeters) 



30.6 



35.7- 



Area of islets (in square milUmeters) 



0.8 



0.6 



The use of the field method is shown in the following figures obtained from the same species : 



Diameter of trunk (in centimeters) 



2.5 



5.1 



25.5 



61.2 



Number of intersections in 2 centimeters .... 



38 



48 



54 



94 



*Stump with water-sprouts. 



TABLE 38. Relation of Size of Vein Islets to Age in Carta alba Koch 



Diameter of trunk (in centimeters) 



22.8 



45.6 



Number of intersections in 2 centimeters 



40 



60-62 







TABLE 39. Relation of Size of Vein Islets to Age in Carta ovata Koch 



1 

 Diameter of trunk (in centimeters) 1 2.5 



3.8 



20.4 



45.6 



Number of intersections in 2 centimeters 



50 



56 



72 



88 



TABLE 40. Relation of Size of Vein Islets to Age in Acer saccharium L. 



Diameter of trunk (in centimeters) 



1.3 



2.5 



30.6 



38 



Number of intersections in 2 centimeters 



42 



52 



80 



88-94 



