Senile Changes in Leaves of Certain Plants 



325 



the kindness of Dr. U. P. Hedrick, of the New York State Agricultural 

 Experiment Station at Geneva, the pedigreed vines growing there were 

 placed at the writer's disposal, and table 45 is based on them.^ The 

 vines of Concord, Worden, Catawba, and Diana were of equal size, and 

 all the varieties were growing under apparently identical conditions of 

 environment. 



TABLE 45. Size of Vein Islets in Leaves of Six Varieties of Cultivated Grapes 



Variety 



Concord. 



Worden (Concord seedling) 



Concord seedling 



Catawba 



Diana (Catawba seedling) . 

 Diana seedling 



Years 

 since origin 



70 

 50 



7 



114 



63 



5 



Age of 

 individual 



plant 

 examined 



14 

 14 



7 

 14 

 14 



5 



Number of 

 intersecting 

 veinlets in 2 

 centimeters 



66 

 58 

 35 

 82 

 74 

 38 



The size of the vein islet in these determinations is evidently related 

 to the time that has elapsed since the last seed propagation. Although in 

 the case of four of these varieties many generations of cutting propagation 

 had intervened, in each of which meristematic tissue had been removed 

 from contact with old speciahzecl tissues, nevertheless the decrease with 

 age in size of the vein islets had progressed in much the same way as 

 if contact with the first individual of the variety had been maintained. 



Further applications of the venation test to cultivated plants will be 

 discussed subsequently in this paper. (See page 351.) 



CONCLUSIONS regarding THE SIZE OF VEIN ISLETS AS EVIDENCE OF THE 

 occurrence OF TRUE SENILITY IN PERENNIAL PLANTS 



The results of this study of the leaf venation of the woody perennials 

 mentioned have demonstrated that the size of the vein islets constantly 

 decreases as the plant grows older. The only physical connection between 

 the leaves of this year and those of past years is the meristematic tissue 



3 The writer desires to thank M. J. Dorsey and R. D. Anthony for their assistance in locating cultivated 

 plants used, and for the data regarding the ages of the varieties and individuals. 



