SOME STEM TUMORS OR KNOTS ON APPLE AND QUINCE TREES. 13 



Apple trees from fifteen to twenty years old badly diseased with 

 these tumors have been observed in various localities in the Missis- 

 sippi Valley. The cores of the tumors ex- 

 tended nearly to the heart or center of the 

 wood of the largest limbs, indicating that 

 the tumors had been present during the life- 

 time of the trees. Upon inquiry, the owners 

 claimed that such trees usually bore as well as 

 other trees in the orchard, and from all indi- 

 cations they were making as good growth as 

 other trees. The knots were apparently sound 

 throughout, and as far as could be observed 

 did no damage to the tree other than to ob- 

 struct the circulation to some extent. This 

 interference with the circulation of the tree, 

 however, can not be considered beneficial to 

 its grow^th. 



Waite, of the Bureau of Plant Industry, 

 has observed in many instances that the cen- 

 ters of old tumors on 

 mature apple trees of- 

 ten decay, either di- 

 rectly as a result of 

 this disease or through 

 the entrance of organ- 

 isms which may seriously injure the tree. 

 The climate and conditions of the Atlantic 

 coast, where Waite made his observations, are 

 different from those in which the writer's 

 observations were made, and this may ac- 

 count in some measure for the different ef- 

 fect observed. 



A study of the effects of the forms of the 

 disease occurring on the roots of the apple 

 tree is in progress and it is hoped that the 

 results may be published later. Some of these 

 results are very peculiar; for instance, the 

 writer was surprised to find, in planting out in 

 an orchard under the same conditions during 

 a very dry season about 700 apple trees, one 

 half of which had roots diseased with hairy- 

 root of the woolly-knot type (fig. 9) and the other half healthy, 

 smooth roots, that a greater stand of trees w^as obtained with the for- 

 mer. The loss in the case of the hairy-root trees was about 19 jDer cent, 



[Cir. 3] 



Pig. 10. — The simple form of 

 hairy-root on an apple 

 seedling grown in an ex- 

 periment. 



Fig. 11. — The origin of 

 hairy-root from buds on an 

 apple seedling. 



