230 THE " SHOT-HOLE " FUNGI OF STONE-FRUIT TREES, 



was not due to any peculiarity on the part of the fungi, but to a 

 peculiar reaction of the plant to the injuries received. Spraying 

 experiments with chemicals such as formalin and corrosive sub- 

 limate showed that similar results followed from their use, and 

 from these experiments and other observations the author arrived 

 at the conclusion " that the shot-hole eflfect of plums, peaches, 

 cherries, &c., is a peculiar reaction of the plant to injuries such 

 as may be produced by many fungi, b}^ certain chemical reagents 

 and possibly by other causes." 



It has already been shown that at least twenty different 

 species of fungi produce shot-hole effects, and this result seems to 

 be due to an effort on the part of the plant to throw off the 

 irritant, whatever it may be. It is not to be inferred, however, 

 that the spotting of the leaves can develop into "shot-hole" only 

 in the genus Primus, although it is so very marked there. I have 

 observed the cumulative effects of a fungus [Phyllosticta 

 pelargonii, n.sp.) for some years on an Ivy-leaved Pelargonium. 

 For several years the leaves had been spotting badly, and this 

 season actual shot-hole was produced just as bad as in the Plum 

 or Peach-leaves. 



Apple and Apricot "Shot-hole" contrasted. 



The great Australian shot-hole fungus, Phyllosticta prunicola, 

 attacks the Apple as well as the stone-fruit trees, and it is inter- 

 esting to note the different ways in which the fungus affects the 

 Apricot and the Apple-leaf, for instance. In the Apricot-leaf there 

 are generally produced, as the final effects of the fungus, distinct 

 round holes, as if small shot from a gun had passed through, and 

 the margin of the hole is neatly and firmly rounded off by the 

 callus or healing tissues. The wound is thus healed, the cause of 

 the mischief is thrown off, and the injury is restricted as much as 

 possible. In the Apple-leaf, on the other hand, there are minute 

 round or irregular brownish spots produced, generally surrounded 

 by the ruddy-brown margin, as in Apricot, but large surrounding 

 portions are discoloured besides. The spot gradually becomes 

 thinner and thinner, as if excavated from above and below, until 



