Senile Changes in Leaves of Certain Plants 



317 



It is possible that many of the cuttings came from vines on the boundary 

 lines of the age groups, instead of being evenly distributed throughout 

 the whole range of each group; but, in spite of this, the inherent effect of 

 the age of the vine is plainly seen. 



METHOD FOR DETERMINING APPROXIMATE AGE BY MEASUREMENT OF 



VEINAGE 



In addition to the foregoing investigation, hundreds of field measure- 

 ments of the relation between the size of islets and the age of the vine were 

 made, in five different summers, about 

 Cincinnati and Ithaca. The method 

 used was simple, and well adapted to 

 the practical nurseryman and fruit 

 grower. A paper clip (called the cub 

 tiger clip) was procured and a dis- 

 tance of two centimeters marked along 

 the jaws. A piece of the leaf to be 

 examined was torn out from between 

 two large secondary veins, held by the 

 clip toward the light, and examined 

 with a pocket lens. The number of 

 veinlets intersecting the edge of the 

 jaw in a distance of two centimeters 

 was counted in several places on the 

 leaf and the average was taken. The 

 result of these observations showed that such an average gives a rough 

 approximation of the age of the vine on which leaves have grown, as 

 indicated in table 27: 



1 120 



, 



Pulse rate 

 minute 



CO o 

 o o 



XB 



of vein islets 

 are millimeters 



p p 

 t-o w 

 o o 



\A 







10 20 30 40 50 60 

 • Age in years 



Fig. 57. — Curves showing (A) senile decrease 

 in size of vein islets in leaves borne by cut- 

 tings of Vitis vulpina, and {B) senile de- 

 crease in pulse rate in human beings 



TABLE 27. Field Method of Determining the Approximate Age of Vitis vulpina 

 'Vines from the Size of the Vein Islets in the Leaves 



Number of veinlets 

 intersecting a straight 

 line in two centimeters , Corresponding age of vine 



30 to 35 5 years or less 



35 to 45 5 to 15 years 



45 to 50 15 to 35 years 



50 to 75 35 years and upward 



