I,EAP Curl and Plum Pockets. 325 



the following spring grows out with the developing leaf, multiply- 

 ing more abundantly in certain portions than in others at times. 

 This accounts for the fact that the whole area of the leaf is not at 

 all times affected. 



The persistence of the mycelium during the autumn and winter 

 seasons in the leaf buds is probably the chief cause of the spread 

 of the disease. When buds are taken for "budding" young 

 seedlings in the nursery, if they are taken from an affected tree 

 the disease is quite sure to be transmitted to every young tree 

 which is started from a bud which contains the perennial mycel- 

 ium. Since all of the affected leaves fall off from diseased trees 

 at quite an early period, and at the time of budding the seedlings 

 in August there is probably no sign of the curl in any of the 

 leaves, it would be impossible to discriminate between the dis- 

 eased and healthy trees, or the affected and free branches. An 

 early selection of healthy trees for budding purposes would pre- 

 vent the transmission of the disease through nursery stock. 



Some experiments have been made in various places by spray- 

 ing the trees with the Bordeaux mixture for the prevention of the 

 leaf curl of peach trees. Some of the experimenters reg!&rd it as 

 certain that the disease can to some extent be checked by this 

 method. It is quite likely that, in some cases at least, another 

 disease is confused with the leaf curl, and this fact might account 

 in those instances for the results claimed. More definite experi- 

 ments with an accurate determination of the diseases present 

 should be made before too much can be claimed for the efficacy of 

 the application of sprays for the prevention of this trouble. 



The asci are developed on both surfaces of the leaf. Before 

 the young asci pierce through the cuticle in their development 

 they frequently raise the cuticle somewhat when it appears on 

 drying as a thin whitish glistening membrane. The asci are 

 nearly cylindrical, sometimes slightly clavate, and rounded or 

 truncate at the free ends. They measure 25^-40 long by 8-1 1 in 

 diameter, the larger number possessing intermediate measure- 

 ments and being 30-35 by 9-10. The stalk cells are 6-8 high 

 and 6-9 or 10 in diameter. They frequently taper considerably 



* Measurements where uot otherwise stated are given in terms of the 

 micromillimeter. 



