Senile Changes in Leaves of Certain Plants 



351 



of cultivated plants as a practical and convenient method for the deter- 

 mination of the degree to which senile degeneration is present in any 

 specific plant or variety of fruit. Whether it is also apphcable as a test 

 for the effect of apogamy has not been investigated. 



While the purposes of this paper do not include the apphcation of its 

 findings to vegetatively propagated cultivated fruits, a few examinations 

 of the venation of the leaves of certain varieties were made as prelim- 

 inary tests and the results are given in table 59. The results obtained in 

 the case of six varieties of grapes have already been stated, but for conven- 

 ience mil be repeated in the table. All plants examined were pedigreed 

 plants growing in the orchards of the New York State Experiment Station 

 at Geneva, New York, to which the writer had access through the kind- 

 ness of Dr. Hedrick and his assistants. 



TABLE 59. 



Size of Vein Islets in Several Varieties of Fruits Propagated by 

 Cuttings 



Variety 



Number of 



years since 



origin 



Age of plant 

 examined 



(years) 



Number of 



intersecting 



veinlets in 



2 centimeters 



Concord grape 



Worden (Concord seedling) 



Concord seedling 



Catawba grape 



Diana (Catawba seedling) 



Diana seedling 



Lady apple 



Baldwin apple ■ 



Hubbardston apple 



Hubbardston seedling 



Seckel pear 



Seckel seedling 



St. Catherine plum 



Italian Prune plum 



Green Gage plum seedling 



Jefferson plum seedling 



Red Cheek (Red Cheek Melocoton) peach 



Late Crawford peach 



Elberta peach 



70 



50 



7 



114 



63 



5 



300 



92 



82 



15 



100 



7 



215 



100 



15 



2 



100 



50 



25 



14 

 14 



7 

 14 

 14 



5 

 18 

 18 

 18 

 15 

 20 



7 

 10 

 10 

 15 



2 



8 



66 



58 



35 



82 



74 



38 



49+ 



41 



45 



30 



54+ 



38 



52 



48 



33 



16 



85+ 



53 



41 



In the cases of the Seckel pear and the Red Cheek peach the veinlets 

 were too intricately branched to be accurately counted. 



