ENTOMOLOGY. 



411 



roundish spaces, each with a slight depression in the middle. If we 

 make a section through the knot a year after it could first be seen 

 (in the fall), we can see under each roundish space a white spot, 

 which indicates a cavity in the black tissue of the knot (Fig. 1, d). 

 This cavity is filled with slender, colorless, microscopic threads. 

 Later club-shaped bodies (Fig. 1, e) appear ainong these threads, in 

 w^hich are produced eight colorless winter-spores, which ripen and 

 are able to germinate about the end of January or February. These 

 winter-spores eventually escape and carry the disease to other 

 plants of the same genus. Such winter-spores (Fig. 1, /) I have re- 

 peatedl}^ sown in water, and they begun to germinate very quickly, 

 growing into germ-tubes. Some brown spores found with the win- 

 ter-spores grew even more rapidly and became quite long in two 

 days. Summer- spores sown upon gelatine change to an elliptical 

 form, germinate and produce a felted patch; later this becomes 

 dark, and soon afterwards forms erect threads, bearing spores. 



As this disease is caused by a plant fully as injurious to the horti- 

 culturist as the Canada thistle and Russian thistle is to the farmer, 

 there is no reason not to have some laws enacted to prevent its 

 further increase and injury. The knots are readily seen, and can as 

 readily be reinoved; and as by removing and burning them we can 

 soon control this vegetable pest, it is about time that we should 

 have laws to that effect and enforce them rigidly. 



Plum Pockets, or Bladder Plums (Fig. 2). 

 (Taphrina pruni, Tul.) 



Fig. 2. Plum Pockets, or Bladder plums ; a, bladder, nat. size; b, mycel- 

 ium entering plant; c, mycelium forcing its way through epidermal layer; d, 

 e, asci; e, spores, all greatly enlarged. 



There are few diseases of plants which attract so much attention 

 as this one. Wherever plums are grown, both of the cultivated and 

 wild kinds, this disease appears from time to time, not seldom de- 

 stroying the whole crop. As very often small reddish maggots oc- 

 cur inside these bladders, many people imagine that insects have 



