290 Harris M. Benedict 



plasm than have the speciaHzed cells which develop from them, and thus, 

 according to the views of Minot and Hertwig, the former would be paten- 

 tially younger; but that is not the point at issue. The real issue is, pro- 

 vided always that the evidences of senile deterioration found in animal 

 cells may serve as a guide to senihty in plant cells, whether the meris- 

 tematic cells of the older perennial differ from those of the seedhng in this 

 or in other respects. 



It may be advisable to again refer at this point to an argument which 

 possibly has had some weight; namely, that the very great age attained 

 by certain trees is an indication that they must be immune from senility 

 as this is known in animals. Some of these trees have lived for five 

 thousand years, or many times the age to which man has attained. This 

 argument can be applied to the human being with most interesting and 

 reassuring results. The rotifer Pleurotricha haffkini, studied by Metch- 

 nikoff (1908), has a total span of life of three days. Applying the 

 above argument, a child who reaches the age of three months, having 

 existed forty times as long as another organism, may be assumed to be 

 immune from the stern decree of senile laws. The elephant Kves one 

 hundred thousand times as long as the rotifer; and in general the extra- 

 ordinary differences in duration of life found in animals in which undoubted 

 senility occurs, robs the fact that plants in general are possibly longer-lived 

 than animals of any significance as regards senility. 



INVESTIGATIONS ON SENILE CHANGES IN LEAVES OF VITIS VULPINA L. 

 AND CERTAIN OTHER PLANTS 



PLAN OF INVESTIGATION 



It would seem that the logical method of attacking the problem is by 

 a careful comparision of the same organ in young and old plants of the 

 same genus for evidences of senile deterioration in structure or function. 

 It was considered desirable to choose a plant that was marked by extreme 

 vigor in putting forth new growth each year, in order to minimize as 

 much as possible the chance of the presence of unfavorable conditions 

 other than age. The wild grape, Vitis vidpina L., answered this require- 

 ment. Any one who has noticed the long shoots and luxuriant foliage 

 produced by this vine each spring must feel that the conditions for its 

 nutrition and general health are good, and that the harmful results usually 

 ascribed to the increasing size of a plant are not in this case serious. 



