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BITTER PIT INVESTIGATION. 



XIX.— DEGENERATION OF APPLE TREE VARIETIES. 



It is sometimes stated that Bitter Pit is due to deterioration or degeneration in the varieties 

 subject to it, and it becomes necessary, therefore, to consider the supposed degeneration of varieties 

 as one of the possible causes of the trouble. 



Every now and again the subject of degeneration in cultivated plants crops up, which shows 

 itself in the quantity and quality of the produce diminishing and individual varieties actually 

 dying out. It is contended that when varieties have been cultivated for a considerable period 

 their original vigour becomes reduced, a weakness due to old age sets in, and that the variety, like 

 the individual tree, for instance, has a limited duration of life. We have to distinguish here between 

 varieties which are propagated in a sexual way by means of seed, and such as our fruit trees which 

 are mainly propagated in a non-sexual or vegetative way by means of buds or grafts. Our 

 varieties of apple trees have originated as a rule from seedlings, and from the original tree, branches 

 or buds have been taken to multiply it. 



In the case of a favorite variety of apple, such as Jonathan, innumerable buds or grafts 

 must have been taken from tree after tree, and thus the numerous progeny of this variety have 

 descended from a single individual. And just as each individual has a limited duration of life, so 

 it is argued must the variety which is just composed of the detached portions of one original tree. 

 Some orchardists believe that the older varieties of apples are becoming more and more feeble, and 

 that new varieties are required to replace them, and the Baldwin apple is a case in point. 



Those who support the theory of degeneration are able to point to various cultivated plants 

 which seem to bear it out. Thus the old varieties of potatoes, which were extensively cultivated 

 and very prolific, are now no longer seen on the market, and even in cereals the good old sorts are 

 being replaced by new ones. 



In the Gardeners' Chronicle for 1875 the question was discussed — Do varieties wear out, or 

 tend to wear out. And the two extremes are presented there of limited and unlimited duration of 

 life. Thomas Andrew Knight, a distinguished President of the Horticultural Society of London, 

 upheld the view that all varieties are of very limited duration, in opposition to Speechley's dictum 

 that " Apples properly planted will retain their good qualities so long as sun and earth endure." 

 Eminent botanists, however, such as Lindley and De Candolle, maintained that this rapid dying 

 out did not occur, since there are so many old varieties which remain, the Eibston Pippins, for 

 instance, being to all appearance as good as ever they were, and numerous varieties of great age, 

 well known to the practical horticulturist, are still healthy and productive. In attempting to answer 

 the question, however, a distinction must be made, as already pointed out, between varieties pro- 

 pagated by seed, purely bred and not crossed, and varieties propagated from buds, cuttings, grafts, 

 tubers, &c. Dr. Asa Gray inclined to the opinion that the former did not tend to run out in time, 

 since the older a race is the more reason it has to continue true, while the latter would probably do 

 so. He sums up as follows : — " The conclusion of the matter from the scientific point of view is 

 that sexually propagated varieties or races, although liable to disappear through change, need not 

 be expected to wear out, and there is no proof that they do ; also, that non-sexually propagated 

 varieties, though not liable to change, may theoretically be expected to wear out, but to be a very 

 long time about it." 



Downing has a chapter on " Eemarks on the duration of varieties of Fruit Trees." After 

 referring to the popular notion that when a good variety of fruit was once originated from seed, it 

 might be continued by grafting and budding for ever, he expresses the opinion that, practically, no 



