Senile Changes in Leaves of Certain Plants 



315 



of the rank of the veinlets in leaves borne by cuttings of Viiis vulpina 

 of different ages shows the following results: 



TABLE 25. Rank of Veinlets in Immature Leaves Borne by Cuttings of Vitis 

 VULPINA OF Different Ages 



Position of leaf 



Enclosing 

 veinlets 



Penetrating 

 veinlets 



Vine twelve years old 



First leaf on cuttings 



Second leaf 



Third leaf 



Fourth leaf 



Fifth leaf 



Sixth leaf 



Seventh leaf 



Vine twenty -six years old 



5th rank 

 6th rank 

 6th rank 

 6th rank 

 7th rank 

 7th rank 

 7th rank 



6th rank 

 7th rank 

 7th rank 

 7th rank 

 8th rank 

 8th rank 

 8th rank 



First leaf 



6th rank 

 7th rank 

 6th rank 

 7th rank 

 7th rank 

 8th rank 

 8th rank 



7th rank 



Second leaf 



8th rank 



Third leaf 



7th rank 



Fourth leaf 



7th rank 



Fifth leaf 



8th rank 



Sixth leaf . 



9th rank 



Seventh leaf 



9th rank 







The important fact is evident from table 25 that in the leaf from the 

 older vine the vein islets have been divided by the development of an 

 additional rank of veinlets, and each division has been partly penetrated 

 by veinlets of still higher rank. The fact that size relationship of the 

 vein islets holds for the immature leaves of old and young vines as definitely 

 as it does for the mature ones, which have been subjected to the various 

 external factors of environment, is further evidence of importance support- 

 ing the claim that the difference in size of the vein islets is due to a con- 

 stitutional rather than to an environmental cause. 



In May, 1910, another set of cuttings was started, this time in pre- 

 pared soil. These cuttings were obtained and started for the writer 

 by an assistant, and the grouping was somewhat different from that 

 used in the first series. All the cuttings were grown in the same box 

 of prepared soil and all environmental conditions were identical for 



