SOME STEM TUMOES OK KNOTS ON APPLE AND QUINCE TREES. 11 



bundles of woody tissue are mingled abnormally with small patches 

 of parenchymatous tissue. Springing from the surface of each of 



Fig. 7. — Longitudinal section of 

 a tumor on an apple limb after 

 throwing out roots when placed 

 in soil. 



Fig. 8. — Longitudinal section of woolly-knot on a 

 root-grafted apple tree grown from apparently- 

 healthy scion and root. 



these forms are numerous fleshy roots which are often fasciated and 

 distorted. These fleshy roots as they grow older either rot away in 

 part or become woody. 



RELATION OF THE TUMORS TO OTHER FORMS OF DISEASE. 



With our present knowledge, therefore, and as a result of the ob- 

 servations and experiments previously mentioned, these tumors on 

 the limbs and trunks of apple trees may be considered the same disease 

 as the woolly-knot form (fig. 9) of hairy-root; in other Avords, they 

 are the aerial form of hairy-root. The simple form of hairy-root, 

 which was described first by Stewart, Rolfs, and Hall ^ and men- 

 tioned later by the writer ^ as a form of disease distinctly different 



« Stewart, F. C, Rolfs, F. M., and Hall, F. H. Geneva, N. Y., Agricultural 

 Experiment Station Bulletin 191, pp. 300-301 and pi. 2, 1900 ; also Geneva, N. Y., 

 Agricultural Experiment Station Report 19, pp. 176-178 and pi. 23, 1901. 



^ Hedgcock, George G. The Crown-Gall and Hairy-Root Diseases of the Ap- 

 ple Tree. Bureau of Plant Industry Bulletin No. 90, Part II, pi. 2, fig. 1, and 

 pi. 3, fig. 2, 1905. 

 LCir. 3] 



