318 



Harris M. Benedict 



While this method is, of course, not so fres from error as the photo- 

 graphic method — since only a fraction of the actual number of islets 

 are measured and a hneal instead of an area calculation is employed — 

 still it is a practical method for general use in field, nursery, and orchard, 

 such as was originally sought. 



In about one per cent of the several hundred field determinations made 

 and checked by ring counts, serious discrepancies were found. It is pos- 

 sible that these exceptional vines were examples of such extreme varia- 

 tions as are sometmies found in other specific morphological characters. 

 A number of other species of perennial plants were examined, and it was 

 found that, while the size of vein islets always diminished with age, the 

 actual size of the islets at any age was a specific character relatively con- 

 stant in each species. Such individual abnormal plants as those- mentioned 

 above resemble other species in the character of their venation. 



COMPARISON OF SIZE OF VEIN ISLETS IN PLANTS OF DIFFERENT AGES, IN 

 VITIS BI COLOR AND CERTAIN OTHER PLANTS 



The results of a preliminary investigation of the relation between age 

 and venation in some woody perennials other than Vitis vulpina are 

 given in the following pages. 



Size of vein islets in Vitis bicolor Le Conte 

 The vines used for these measurements were not transversely cut, and 

 the only guide that could be obtained to their relative ages was the 

 diameter of the stems. They were all growing in the same small area, 

 under apparently identical conditions. 



TABLE 2S. Area of Vein Islets in Leaves of Vitis bicolor, Vines 1 and 2 



Number of leaf 



Length 

 (centimeters) 



Breadth 

 (centimeters) 



Area 



(square 



centimeters) 



1 



2 

 3 

 4 



Vine 1 

 17 

 18 

 16 

 18 



25.5 centimeters in diameter 



18 

 17 

 15 

 18 



200 

 210 

 170 

 220 



Weight 

 (grams) 



Area of 



islets 



(square 



millimeters) 



2.0 



2.7 

 2.6 

 3.5 



0.2276 

 0.2298 

 0.2909 

 0.2391 



