322 



Harris M. Benedict 



In this case, as in the case of Vitis vulpina and V. hicolor, the more 

 rapid decrease in size of vein islets in the early years is to be particularly 

 noted. The significance of this will be discussed later. 



Another interesting observation was made with these specimens of 

 Tecoma radicans. Among the seedlings that sprouted around the parent 

 vines, root shoots from the old vines were found growing. The connection 

 of these root shoots was estabhshed by examination. Although seedhngs 

 and root shoots seemed equally vigorous and could not be distinguished 

 from each other at first sight, a venation count successfully separated 

 them, since the root shoots all showed in their leaves the size of vein islets 

 characteristic of the parent plant, while those of the seedlings were much 

 larger. This fact is of considerable importance in its bearing on the cause 

 of these differences, as will be indicated later. 



Size of vein islets in several kinds of trees 

 The following data, as is evident, represent nothing but a comparison 

 of a few trees of different ages that were growing under similar external 

 conditions, and the results are interesting merely as a corroboration of 

 the effect of age in decreasing the size of vein islets in perennials: 



TABLE 33. Relation of Size of Vein Islets to Age in Salix nigra Marsh 



Diameter of trunk (in centimeters) . 



Area of islets (in square millimeters) 



2.5 



0.55 



15.3 



0.4 



38.1 



0.3 



The largest tree was probably the parent of the others, as they grew in an isolated place. 

 TABLE 34. Relation of Size of Vein Islets to Age in Castanea dentata Borkh. 



Diameter of trunk (in centimeters) . . 



5.1 



12.7 



25.5 



61.2 



91.2 



Area of islets (in square millimeters) . 



1.0 



0.7 



0.5 



0.4* 



0.3 



* The tree 61 .2 centimeters in diameter had been cut down, and the leaves examined were very large ones 

 borne on luxuriant water sprouts. 



TABLE 35. Relation of Size of Vein Islets to Age in Quercus alba L. 



Diameter of trunk (in centimeters) 



0.7 



40.8 



38.0 



Area of islets (in square millimeters) 



1.5 



0.3* 



0.3 



* The leaves examined were much larger than normal size, being borne on luxuriant water sprouts. 



