308 STATE HORTICULTURAL SOCIETY. 



disease. Each of the pimples contains a large number of spore cases or 

 asci, in each of which about eight spores are contained. 



Any person who has once seen a knot should be able to recognize them, 

 as, not only are they well marked when in their summer and winter fruit- 

 ing stages, but the appearance of the knots at any time is distinctive. 

 There are several other forms of spores, but the conditions under which 

 they develop is not certainly known. 



When a knot has once commenced to form, no treatment with copper 

 compounds can afEect it, but it is likely that, if the trees are kept well 

 covered, the spores will not be able to gain entrance. 



The only safe thing is to watch the trees and cut off the knots whenever 

 they appear. If they can be taken in hand in the spring, when the swell- 

 ing first starts, and before the summer spores form, little harm will be 

 done. The trees should be watched carefully during the summer, and 

 should be examined at least once after the leaves have fallen, as the knots 

 can then be more easily seen and, if they are cut off at any time before 

 January, the winter spores will not have developed. In cutting off a 

 branch, care should be taken that it is removed several inches below where 

 the knot shows, in order that all of the mycelium of the fungus may be 

 removed. If this is not done, the knot will be likely to show the coming 

 spring below where the cut was made. Sometimes the knots are ifpon the 

 trunks or large branches, which can not be taken off without injuring the 

 trees seriously. If such is the case, it will be well to attempt to save the 

 tree or branch, if the knot has not become too old and hard. The swelling 

 should first be pared off and tincture of iodine applied; this will follow the 

 threads of the fungus and destroy them. The wound should then be 

 painted with lead and oil paint, which will both aid in killing the 

 fungus and preventing the drying out of the tissues. 



In 1893 a law was enacted in connection with the " yellows " law, which 

 provides for the destruction of the knots, in case the owners refuse to 

 attend to it, under the direction of the commissioners. 



The plum -growing industry is becoming of much importance in many 

 portions of the state, but it is likely to be of short duration if the black- 

 knot makes its appearance in the orchards, unless the law is rigidly 

 enforced. 



LEA.F SPOT (CylindrosporiumZpadi, Karet). 



This disease, often spoken of as leaf blight and shot-hole fungus, and 

 which formerly was described as Sejitoria cerasina, has been one of the 

 most troublesome to the grower of the plum as well as of the cherry. It 

 is quite generally distributed and often causes the winter-killing of 

 thousands of trees, which through the loss of their leaves in August are 

 unable to ripen their wood. 



It shows first as small, purple spots, upon both sides of the leaves, and 

 in a short time the tissues attacked take on a brown color. These affected 

 spots frequently drop out, leaving small, round holes, whence one of the 

 common names of the disease. With a lens it can be seen that there are 

 one or more black dots on the under surface of the spots. These are the 

 fruiting pustules within which the spores are produced in great numbers. 

 The spores are long and slender and generally contain a number of cells. 

 Each cell of these summer spores is capable of propagating the fungus. 



