SOME STEM TUMOES OR KNOTS ON APPLE AND QUINCE TREES. 



9 



name of Kropfmaser, with which form of disease they may be 

 identical. A similar form on Pirus malus chinensis has been de- 

 scribed b}^ Kissa." 



On the quince tree the disease originates quite similarly to that 

 already described on the apple tree, with the exception that tumors 

 have not been noted affecting the end and base of small twigs. The 

 disease appears first in the form of small swellings on various por- 

 tions of the limbs and twigs of the trees. In a year or two the 

 fleshy bark of these is broken open by the formation of numerous 

 root-like structures, and the tumors assume a black, roughened ap- 

 pearance, but resemble greatly in 

 structure the older forms described 

 on the apple tree. These peculiar 

 outgrow^ths (fig. 2) are often very 

 numerous on the limbs and trunks 

 of quince trees. 



EXPERIMENTS. 



A number of limbs diseased simi- 

 larly to those shown in figure 2 

 were taken from quince trees at 

 Chico, Cal., and others similar to 

 those shown in figures 1, 3, and 4 

 were taken from an apple tree at 

 Fayetteville, Ark., and entirely cov- 

 ered with moist soil at the Mis- 

 souri Botanical Garden, St. Louis, 

 Mo., during the month of March, 

 1906. After these had been covered 

 with moist soil for about four 

 weeks they were taken out, and a 

 number of the tumors had pro- 

 duced roots in abundance from the 



surface (figs. 5 and 6), but no roots were thrown out from any other 

 portion of the limbs. In the case of the apple limbs each of these 

 knots, after they had developed roots from 1 to 2 inches in length 

 from further growth in the soil, agreed in appearance and structure 

 with the knots occurring in connection with one form of the hairy- 

 root disease of the apple, known as the woolly-knot form (see fig. 9). 



In February, 1907, scions were taken from the Charlamoff tree pre- 

 viously mentioned, some of which contained knots or tumors like those 



Fig. 4. — Older tumors than those shown 

 in figure 3 on a Charlamoff apple tree 

 at Fayetteville, Ark. 



<^ Kissa, N. W. Kropfmaserbildung bei Pirus malus chinensis. 

 fur Pflanz^nkranl^heiten, vol. 10, pp. 129-132 and 2 plates, 1900. 

 [Cir. £] 



Zeitschrift 



