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FRUIT BOOK. 



ant in growth, as to require immoderate pruning to 

 keep them within due bounds ; and excessive prun- 

 ing, in such cases, only tends to aggravate the evil." 

 Plum trees are subject to a disease which has been 

 so destructive to them, as to have destroyed nearly 

 all the damson plums heretofore so common in our 

 neighborhood. It appears at first a greenish brown 

 excrescence, which soon becomes black. Various 

 are the hypotheses which have been given as to the 

 cause of these warts. Some have attributed it to 

 the quality of the soil, others to a redundance of 

 nourishment, which distend the cutaneous vessels by 

 an extravasation of the sap ; others to a much more 

 rational and philosophic solution, attributing it as the 

 work of an insect. In our examinations, &c. for 

 fiye years on this subject, it was not until the spring 

 of 1843 that we were able to find an insect in these 

 excrescences while in a green and fresh state ; and 

 have heretofore been inclined to adopt the theory of 

 the distension of the cutaneous vessels, considering 

 the worms which we have repeatedly found in these 

 warts, when black, to be a consequence and not a 

 cause of this disease. We now consider this excres- 

 cence analogous to that which we find upon the 

 swamp pink, or azalea, called by boys swamp apples, 

 which has always been supposed by botanists to be 

 caused by an insect. The only remedy that we 

 have found effectual has been the amputation of the 

 diseased limb. These excrescences always extend- 

 ing themselves upwards, and not downwards, upon 

 the branches, would seern to prove that the disease 



