The Canadian /fortictiltiuisL 



121 



PLUM POCKETS-(TAPHRINA PRUNI.) 



THIS disease is due to the pres- 

 ence of a parasitic furif^us whicli 

 attacks the yoiin<( fruit, and by its 

 f,ao\vth\vithin tlieir tissues causes the 

 pecuHar development of the latter 

 which finally results in the formation 

 of the so-cailcd " pocket." 



The " pockets " (fig. 77) make their 

 appearance soon after the flowers 

 have fallen, attain their full size and 

 drop from the tree towards the mid- 

 dle or last of June. At first they are 

 more or less globular in shape, but 

 as they grow older they become 

 oblong or oval and frequently more 

 or less curved. They vary in size, 

 but as a rule are from i to 2 inches 

 in length and from one-half to one 

 inch in diameter. When young 

 they are nearly smooth and can be 

 distinguished from the health}' fruit 

 by their pale yellow or reddisli color. 

 As they grow older the color changes 

 to grey, the surface appearing as 

 though it had been sprinkled with 

 fine powder, and at the same time 

 the " pockets" 

 become wrinkled, 

 l-'inally they turn 

 black or dark- 

 brown, and rattle 

 like bladders 

 wlien brought in 

 contact with any 

 hard substance. 

 vio.77. Sections through 



the diseased fruit show that the walls 

 are quite thick, and that in place of 

 a stone there is a large cavity filled 

 with fungous threads and air. 



The fungus attacks the joung 

 branches and leaves, and when this 

 occurs the injury is, of course, much 

 greater than when the fruit alone is 

 attacked. 



The disease never sweeps over the 

 country attacking all varieties of the 

 phun alike, but, on the contrary, it 

 often happens that a particular tree 

 will bear nothing but " pockets," 

 while adjacent trees of the same 



variety, grown under precisely the 

 same conditions, show no traces of 

 the disease whatever. As a rule, a 

 tree that has once borne a crop of 

 "pockets" seldom recovers, but con- 

 tinues with each succeeding year to 

 produce a greater or less number of 

 the malformations. 



All plums are more or less subject 

 to the attacks of this parasite, but it 

 is usually more abundant on the red 

 and purple varieties. It occurs also 



" Plim PocKKTs." Fig. ,-b. 



on the wild red and the beach plums, 

 and on the dwarf, the wild black and 

 the choke cherries. 



A microscopic examination of one 

 of the diseased plums will show that 

 the fungus occurring within the 

 tissues consists of three parts, name- 

 ly, (i) mycelium ; (2)asci; (3)sporesor 

 reproductive bodies. The mycelium 

 consistsof colorless septate filaments. 

 These are particularly abundant 



