THE PLUM. 123 



and others, that the slight!}- elevated projec- 

 tions, which give to the surface of the knot a 

 pimply appearance, are spores, which ripen in 

 Ma}' and are thrown off to find a lodgment on 

 other branches. Here the growth is slight 

 until the spring following, when the develop- 

 ment becomes very rapid. During the month 

 of June following, the diseased growth pre- 

 sents a dark olive green color. This is due to 

 a vast number of reproductive spores which 

 are thrown off, after which the fungus con- 

 tinues active in the knot to mature the crop 

 of spores for the following May. After this 

 May crop the fungus dies, and the knot be- 

 comes a mass of dead tissue and a harbor for 

 various injurious insects. Thus it appears "that 

 the fungus has a life of two seasons, throwing 

 off its first crop of spores a year after lodg- 

 ment, and afterwards developing the mature 

 knot and ripening a final crop in May. It 

 will be seen that the removal of the knots 

 after this stage will have no effect in checking 

 the disease. The removals should be in the 

 previous stages of growth. Spraying the trees 

 with the sulphate of copper or the Bordeaux 

 mixture about the first of May, and again in 

 three or four weeks, will destroy the spores 

 which are just ripening. But this wUl not 



