260 AMERICAN HOME GARDEN. 



BLACK KNOT. 



This disease, which has almost entirely destroyed the dam- 

 son, the horse plum, and some other kinds, comes at first as a 

 green swelling, bulging out and spreading open with a granu- 

 lated appearance, changing in color till it becomes a black, 

 wart-like excrescence, being, in fact, covered with minute black 

 fungi, which grow and seed upon it. In general, unless ar- 

 rested by cutting out, it continues to spread, either by length- 

 ening itself upon the branch or body, or by breaking out at 

 some other points. When the branch is cut off, the stain of 

 the disease is found extending for some distance below the 

 knot, in the substance of the wood or at the heart. 



It is perhaps more prevalent upon dark-colored plums than 

 on the yellow or green varieties, and has become common upon 

 the sour red and Morello cherries. 



There are variant opinions as to its origin and character, 

 some supposing it to be caused by an insect stinging the bark, 

 various worms being often found in the knots ; others regard- 

 ing it as a vegetable cancer ; but all agreeing that the only 

 method of treating it is to cut it clean off the branches, and 

 perfectly out of the body and limbs in its early stages, and 

 burn every vestige of the cuttings, washing the wounds with 

 brine or a solution of copperas in the proportion of one ounce 

 to two gallons of water, or covering them with grafting com- 

 position or shellac. Perseverance in this course will be found 

 successful in arresting at least its worst results. 



BURSTING. 



The trunks of certain trees, particularly the cherry, some- 

 times open and decay upon the south side, a result attributa- 

 ble to the occurrence of severe frost after the warmth of the 

 sun's rays has started the circulation upon that side. The 

 full sap vessels, we suppose, burst mechanically, as a full wa- 

 ter-pipe is bursted by the same cause. Short stems help to 

 provide against this difficulty, and trees placed so as to re- 

 ceive the slightest shade are seldom harmed. 



