62 MASS. EXPERIMENT STATION BULLETIN 441 



R were still alive. Later in the summer all the trees of this hitherto normal strain 

 died in typical fashion. This seems to prove that the lethal factor in strain R 

 had passed into strain G and indicates that the lethal factor is of a virus nature. 

 If this is true, no vector is present in our nursery, or the virus can be transmitted 

 only by actually transferring virus tissue to a healthy tree. This is the first 

 indication we have observed that a healthy tree can acquire the lethal factor. 



The observation that Blaxtayman budded on Spy 227 grows vigorously the 

 first year and then dies has been confirmed. Trees of several lethal strains were 

 budded on Spy 227 interstock, on Spy 227-2 and on Spy 227-12. Those with 

 Spy 227-12 roots grew much better than those on Spy 227-2 roots. 



Tree Characters of Fruit Varieties. (J. K. Shaw, A. P. French, O. C. Roberts, 

 and W. D. Weeks.) The examination of fruit-tree nurseries for trueness-to-name, 

 which began in 1921, still continues. This inspection was extended to Tennessee 

 and Alabama last year and in 1947 will extend to Iowa and Kansas, and include 

 about 30 different nurseries. Although many of these nurseries have been ex- 

 amined annually for many years and the misnamed trees eliminated, still new 

 mixtures appear. But these are detected at once, which practically prevents 

 propagation and distribution to growers. New varieties appear and must be 

 studied; thus this project is one that has no end. 



Effect of Orchard Mulches on the Plant Nutrients in the Soil. (J. K. Shaw 

 and W. D. Weeks, in cooperation with the Chemistry Department.) This proj- 

 ect has been interfered with by the war. Soil samples were taken this year and 

 the hay mulch applied. The trees with hay mulch look the best and the un- 

 mulched trees the poorest. Further comments on this project may be found in 

 the Report of the Chemistry Department. 



The Nature of Winter Hardiness in the Raspberry. (J. S. Bailey, A. P. French, 

 and R. A. Van Meter.) It seemed possible that there might be a relationship 

 between the rest period of raspberries and the amount of cold the plants will 

 stand in winter; therefore, a study of the rest period was started three years ago. 

 Each fall during November and December raspberry canes of six varieties were 

 brought into the greenhouse at regular intervals and the time necessary to force 

 the buds into growth was determined. From this work the following conclusions 

 can be drawn: (1) The deepest rest, when the buds are hardest to start, is reached 

 about November 1. (2) The time at which the deepest rest is reached is dependent 

 on both the variety and the season, but the season is the more important factor. 

 (3) The buds come out of the rest gradually, the rate depending mostly on the 

 variety and to a lesser degree on the season. (4) The time the buds are through 

 the rest period depends largely on the time they went into the rest and hence on 

 the season. It depends to a lesser extent on the variety. (5) Those varieties 

 which are most resistant to winter cold are usually the slowest to come out of 

 the rest period. This suggests a relationship between rest period and cold re- 

 sistance. Varieties which are least irritable, that is, are least apt to be started 

 into growth during warm periods in the winter, are most cold resistant. 



Blueberry Culture. (J. S. Bailey.) The attempt to control mummy berry by 

 spraying with Fermate was continued in 1946. Some bushes received six, some 

 seven, some eight, and some nine sprays. Primary infection of shoots and blos- 

 som clusters was much lighter than in 1945. There were also fewer mummied 

 berries on the unsprayed bushes than in 1945. Although the differences among 



