350 Hareis M. Benedict 



the original Concord. It is not beyond the bounds of possibihty that some 

 grape grower might confuse such a seed-produced vine with a true Concord 

 graft. The younger vine might be utihzed as a source for cuttings, and 

 these in time might displace the older stock without any one's being 

 the wiser. The possibhty of such propagation was greater in the past 

 than it is to-daj^ and holds for every seed-producing cultivated plant. 

 It is possible, therefore, that some of the seed -producing plants which are 

 cited as conclusive evidence of the harmlessness of long-continued vege- 

 tative propagation have been sexually propagated at intervals. 



The recognition of degeneration in cultivated varieties is rendered 

 difficult by the very long life attained by woody perennials as compared 

 with the hfe of man. Many trees have a natural life spanning several 

 generations of men. Such plants would show httle change in a single 

 generation. The possibility of using the data gathered by the preceding 

 generation as a test of deterioration of fruits to be utihzed by following 

 generations has been practically mipossible in the past. The only criteria 

 of degeneration known in the past have been such characters as yield of 

 fruit and resistance to disease — in other words, characters that are pro- 

 foundly affected by external conditions as well as by internal ones. It 

 is evident that such characters cannot enable the growers of one genera- 

 tion to accurately compare the past and the present conditions of any 

 varieties. Since investigators of to-day cannot make a mathematical 

 summation of the combined effects of all the external factors that are 

 operating throughout a season on a given plant, the inherent- weakness 

 of past comparisons needs no further comment. And yet all the arguments 

 concerning the problem of the effect of vegetative propagation have been 

 based on such comparisons and on theoretical considerations. 



The chief theoretical assumption opposing the idea of degeneration 

 through long-continued vegetative propagation in cultivated fruits has 

 been that of the innnunity of meristematic tissue to senile changes. The 

 results of the present study of the senile changes in the leaves of Vitis 

 vulpina argue against the truth of this assumption. What is of greater 

 importance, in its practical appUcation, is the discovery of specific mor- 

 phological changes in the leaves as the plant grows old, which appear to 

 be independent of external conditions and therefore available for use as 

 tests of the physiological condition of the plant. It is hoped that the 

 change in venation will prove in practice to be appUcable to a wide range 



