Fruit Brevities. 429 



appears to consist of a rich callus over the places of injury, and 

 in the case of bent roots, the growth appears to be an abnormal 

 development of tissues of wood and bark. The younger the root 

 is, which has been bent, the more easily the crevices may appear 

 which lead to the formation of the above mentioned parenchyma- 

 tous wedges; an expansion, of the medullary sheath may occur, 

 and the formation of adventitious buds be induced. . . I have 

 frequently found woody bodies entirely isolated from the woody 

 cylinder of the branches of various trees, especially in apples and 

 in conifers. These bodies were buried in the tissues of the bark. 

 Adventitious buds may be formed easily upon the roots of apples 

 and pears since root cuttings of these plants will frequently pro- 

 duce shoots. Such shoots may also be found upon the more 

 horizontal-growing roots of these trees, even when they are not 

 separated from the parent plant. 



" The formation of root-galls, therefore, does not appear to me 

 more strange than similar swellings which are so commonly seen 

 above ground. At first thought, it would seem strange that these 

 root swellings should appear so much more frequently in certain 

 nurseries. The prevalence of the attacks and the season of their 

 appearance seem to indicate a parasitic origin, but I have been 

 unable to find any plants or animals to which the trouble may be 

 ascribed. The examination of many seedlings from nurseries 

 upon which root-galls had been commonly observed lead me to 

 what I believe to be the true explanation of this disease, which 

 has ajipeared during recent years in so many different localities. 

 Specimens of diseased and healthy roots which were taken from 

 the upper part of the root system show that they have been well 

 nourished and also that they bear many sharp angles, which, in 

 some cases, have led to the growing together of roots that have 

 been closely pressed together. In other cases, it will be seen that 

 the early root system was cut back closely and a great many side 

 roots have been produced near the cut surfaces. Since the young 

 plants, in a vast majority of cases, show by their root systems 

 that they have been well nourished, it may well follow that this 

 good nourishment is also favorable to the formation of root-galls. 



