314 



Harris M. Benedict 



Comparison of the venation of immature leaves 

 In order to determine whether or not the difference in size of vein 

 islets is present from the beginning of the development of the leaf, the 

 venation of a series of leaves from the tips of shoots backward was 

 examined. One examination was made by the photographic method, with 

 the following results: 



TABLE 24. Area of Vein Islets in a Series of Immature Leaves Taken in Order 

 FROM THE Tips of the Shoots Backward, from Vitis vulpina Twenty-five and 

 Ten Years of Age 



Number of leaf 



Length Breadth 



(centimeters) (centimeters) 



Area of vein 



islets 



(square 



millimeters) 



Vine twenty-five years old 



3 

 5 



7 



11 

 11 

 14 

 13 



Vine ten years old 



0.15 

 0.30 

 0.50 

 0.60 

 0.95 

 1.10 

 2.10 

 1.90 



0.010 

 0.015 

 0.022 

 0.058 

 0.090 

 0.120 

 0.150 

 0.190 



1 



3 



3 



0.16 



0.015 



2 



6 



5 



0.29 



0.020 



3 



8 



6 



0.51 



0.027 



4 



9 



8 



0.63 



0.065 



5 



10 



11 



1.00 



0.098 



6 



11 



12 



1.20 



0.150 



7 



14 



17 



2.20 



0.200 



8 



13 



14 



2.00 



0.260 







That this was an entirely typical condition has been shown by many 

 field counts of veinlet intersections by a method explained later (page 317). 

 The sizes of the vein islets in the immature leaves on the cuttings as given 

 in table 23 offer evidence to the same effect. 



If the midrib be called the primary vein, its chief branches secondary 

 veins, the main branches of the secondarj^ veins tertiary, and so on, the 

 final most minute veinlets may be given a definite rank. A comparison 



