THE PARASITIC EXOASCEAE. 



155 



>Yhile the stone, including the embryo, remains stunted. (Fig. 

 49.) The "pocket-plums" (fools or bladder-plums) dry up, and 

 remain hanging on the tree till autumn. De Bary found on 

 the plum a withering of calyx and stamens resulting from the 

 development of the hymenium of this Exoascus ; on the bird 

 cherry, according to Magnus and Wakker, enlargement of the 

 stamens occurs. Sometimes a considerable thickening and 

 twisting of the young shoots takes place, and their leaves 

 curl up. 



EVf '■■■.';■.■ 



Fig. 48. — Exoascus pruni. Twig of Plum, with four deformed fruits ; one 

 normal plum is partially hidden, the other is in the middle. * natural size, 

 (v. Tubeuf del.) 



The mycelium hibernates in the soft bast of the twigs, and 

 proceeds thence in spring into young shoots and ovaries. 

 According to De Bary, the infected ovaries double their size 

 in two days, and are full grown in eight days. The asci form 

 a close layer under the cuticle of the ovary, and finally 

 rupture it. 



