SENILE CHANGES IN LEAVES OF VITIS VULPINA L. 

 AND CERTAIN OTHER PLANTS ^ 



Haeris M. Benedict 



The inevitable onset of senile deterioration after a relatively short period 

 of activity is the basic tragedy of hfe. And j^et, in comparison with the 

 amount of research that has been du-ected toward the discovery of the 

 causes of Hving activities, very httle has been done to determine the causes 

 of the approach of senility. Biologists seem to have tacitly agreed to 

 find out what causes the living machine to run before thej^ seek the reasons 

 why it stops. This attitude has been further encouraged by the belief 

 that the causes of senility could not be understood until the laws governing 

 hving action were determined. 



The work that has been done is natural^ of two kinds — attempts to 

 determine what changes of function and structure are characteristic of 

 the increasing age of an organism, and the promulgation of various theories 

 as to the causes of semhty. So much of the work on senihty has been 

 carried on with animal organisms that this field in plant life may be said 

 to be unentered; the reasons for the neglect of plants in this respect will 

 be dealt with later. It seems advisable, therefore, as the only available 

 basis for approaching this problem in plants, to prepare a brief summation 

 of the results of the investigations on senihty in man and in the lower 

 animals. 



SENILE CHANGES IN ANIMALS 



The chief difiiculty in the search for the changes due to senihty is the 

 constant presence in the hving organism of modifications of tissue and 

 function produced by unfavorable conditions other than age, both internal 

 and external. Much of the work on record has been marred by inadequate 

 appreciation of this fact. Furthermore, the older the organism becomes, 

 the greater is the probabihty that effects of these other adverse influences 

 will be present. It follows, therefore, that the condition of extreme 

 senihty, which has been commonly studied, is actually the most difficult 

 stage to investigate for changes due to age alone. Those theories of 



'Laboratory of Plant Physiology, Cornell University. Contribution No. 15. 



281 



