THE HAMILTON ASSOCIATION. 



91 



of the leaves^ causing them to drop prematurely, 



sometimes as early as the first of August. The 



leaves attacked show at first, scattered here and 



there over the surface, dark purple spots, visi- 

 ble on both sides, varying from one twenty- 

 fourth to one eighth of an inch in diameter. 



After a brief period, the tissue covered by these 



spots becomes dead and brownish in color. On 



examining one of these brown spots under the 



microscope there will be detected from one to 



several minute black points. These are the 



fruits of the fungus, like little capsules, in which 



the spores of the fungus are produced in great 



abundance. These are very slender and many 



times longer than broad, and quite transparent. 



They are usually divided by one or more cross 



walls into two or more cells, and each cell in 



every spore js capable of producing a new growth of this parasitic 



plant. 



Fig. 17 represents a highly 

 magnified section through the 

 leaf, including one of the four 

 capsules, and at a, above, are 

 shown some of the spores, still 

 more highly magnified. The 

 parasite buries itself within the 

 leaf tissue and, therefore, any 

 treatment, to be successful, must 

 be preventative. Spraying the 

 trees with the copper carbonate 

 compounds, or with the Bordeaux 

 mixture, for preventing the plum 

 or cherry rot will result, in all pro- 

 bability, in preventing the growth 

 of this fungus. 



Strawberry Leaf Blight {Sphcerella FragaricE). — This is 

 another of the well known difficulties which meet the grower of 

 small fruits in Ontario. It -is commonly spoken of as the "strawberry 

 rust," "sun scald," or "spot disease," although, according to Prof. 



Fig 17.— Section of diseased plum leaf: 

 a spores. 



