10 SOME STEM TUMOES OR KNOTS OK APPLE AND QUINCE TREES. 



shown in figure 3, while others were smooth and apparently healthy. 

 About 70 per cent contained no knots or tumors ; these were grafted 

 on piece roots from healthy apple seedlings. One hundred of these 

 grafts were planted and grown on the Potomac Flats, near Washing- 

 ton, D. C. The trees gTOwn from these were dug at the end of the 

 season, and G9.3 j^er cent were found to be diseased to a greater or 



^* 



Fig. 5. — Roots produced from 

 a tumor on a cutting taken 

 from a Charlamoff apple tree 

 and kept in moist soil. 



Fig. 6.- — Roots produced from tu- 

 mors on a cutting taken from a 

 Meech quince tree near Chico, Cal. 



less degTee with the woolly-knot form of the hairy-root disease. The 

 remaining trees were apparently healthy, having smooth roots. 

 Those scions which had tumors before planting developed in nearly 

 every instance roots from the tumors, which then agreed in structure 

 and appearance with the woolly-knot form of hairy-root. 



STRTJCTURE OF TUMORS. 



If a section is made longitudinally through one of the tumors 

 taken from the limb of an apple tree after roots have been forced 

 from it hy moisture (fig. 7) and through one of the underground 

 rooted tumors of the woolly-knot form of hairy-root (fig. 8), an 

 identical structure is revealed. The wood elements of both are much 

 distorted and disarranged, growing somewhat in a fan shape from 

 the origin of the tumors near the center of the stem or root. The 



[Cir. 3] 



