348 Harris M. Benedict 



others, send up a multitude of shoots from the roots, while most of the 

 wild trees are limited to seed propagation; and he adds, "Were a tree 

 capable of affording an eternal succession of healthy plants from its 

 roots, I think our woods must have been wholly over-run with those 

 species of trees which propagate in this manner, as those scions from the 

 roots always grow in the first three or four years with much greater rapidity 

 than seedling plants." 



In 1810 Knight pubhshed a paper entitled On the Parts of Trees Pri- 

 marily Impaired hy Age, in which he makes the following statement: 

 " I am, therefore, much disposed to attribute the diseases and debihty 

 of old age in trees, to an inability to produce leaves, which can efficiently 

 execute theh natural office . . . . It is true that the leaves are annually 

 reproduced, and therefore annually new; but there is, I conceive, a very 

 essential difference between the new leaves of an old, and of a j^oung 

 variety." 



Fpllo"^dng Knight's first paper (1795) many observations which agreed 

 or disagreed with his results were reported in Enghsh and Continental 

 horticultural and gardening pubhcations. None of these reports were 

 more than casual notes. 



The first paper of interest aft^r Knight's was that by Jessen (1855), 

 who strongty supported Knight's theoiy and introduced the term sorte 

 to include all the plants grown from the cuttings of a parent plant. 

 He beheved that all the members of a sorte would grow old together. 



In some degree the results of Bouche and BoUe (1875) supported Knight 

 in the case of the cultivated ofive tree. 



The first paper to make a serious attack on the theoiy was that pub- 

 lished by Sorauer in 1877. Sorauer maintained that cuttings showed 

 the same type of differences among themselves that seedfings did, and 

 might serve the same purpose without producing serious degeneration. 



In 1882 Hildebrand pubhshed a long discussion on the duration of 

 Hfe in plants and the effect of various external factors in increasing or 

 decreasing to some degree the constitutional duration. While this paper 

 is full of interesting facts regarding this pomt, it nowhere touches the 

 problem of senihty as affecting constitutional duration, and therefore 

 Hildebrand's results do not du-ectly concern the present study. 



Burgerstein (1895) made some observations on the relation of vegeta- 

 tive propagation to degeneration, arguing against its possibihty. 



