Leaf Curl and Plum Pockets. 329 



Prunus domestica Iv. Plum. 

 Exoasctis pnaii Vxxck&X. 



This fungus forms the well known " plum pockets," or " plum 

 bladders" on the fruit Prunus domestica, the common cultivated 

 plimi. The mycelium is perennial in the fruit bearing branches 

 and from these places grows out into the young ovaries in the 

 spring. All or nearly all parts of the ovary are affected and the 

 fungus stimulates the tissue of the ovary so that a remarkable 

 hypertrophy occurs. The tissues become dry and spongy, the 

 form of the plum being considerably enlarged. No stone is de- 

 veloped in the diseased plums and the interior is hollow and frt 

 quently traversed by loose threads of torn tissue. All of the plums 

 on an affected tree are not usually affected, though I recollect see- 

 ing a tree in Chapel Hill, N. C, in the spring of 1886, on which 

 there was not a single plum free from the disease. Frequently 

 there are plums unaffected in the same cluster with the diseased 

 ones. 



The asci are very closely crowded together and frequently may 

 develop quite irregularly, a few pushing through the cuticle first, 

 followed later by others. A section of an affected fruit at this 

 time would then show some asci very long and mature while 

 others are not quite mature and the spores undifferentiated. 

 There are many cells of the hymenium intermingled with the asci. 

 The asci measure, in specimens which I have seen on P. domestica 

 from Wisconsin, 30-60 long by 7-10 in diamter, and the stalk 

 cells 15-22 high by 3-7 in diameter are rounded, or rarely pointed 

 below. The longer asci are nearly cylindrical and many of the 

 shorter ones slightly clavate. The spores are oval to elliptical, 

 and from 3.5-5 in diameter. The measurements given by Sade- 

 beck show a greater diameter, the ascus reaching a diameter as 

 high as 15, and the stalk cell being given as 8 in diameter. 



Robinson* speaks of a dimorphism in the asci, the slender ones 

 being 43-60 long and 5.5-7 in diameter, while the stouter ones 

 were 27-35 long by 9-12 in diameter. The size of the stalk cells 

 he gives as 12-18 high by 5-8 in diameter. He also notes the 

 fact that nearly all the asci which he examined were more slender 



* Notes on the genus Taphrina. Ann. Bot, I, p. 166-7, 1887-8. 



