THE HAMILTON ASSOCIATION. 8 1 



ports of his work. But, although a large amount of money has been 

 spent in this direction during the last three years, as yet no definite 

 results have been obtained. 



A year ago last summer I had a call from Professor Burrill, of 

 Champaign, III, who was a delegate to the American Association 

 for the Advancement of SciencCj then meeting in Toronto. He was 

 looking up cases of yellows, which he said were not common in his 

 own state. He is a man of most careful research, and his opinions 

 are worthy of consideration. He believed that the disease was 

 caused by bacteria, and in- this most scientific men are in accord 

 with him. 



One thing we do know about the yellows, and that is that it is 

 of an infectious character, in which respect it equals scarlet fever 

 and small-pox. It may be carried from tree to tree, either by the 

 bees in their searches for honey, or by instruments used in pruning 

 the orchard. 



We may hope, however, that ultimately the mystery will be 

 solved, for the Pear Blight was, until lately, quite as mysterious. 

 This latter has been the terror and despair of pear growers in all 

 parts of the country. It would come in a single night upon the 

 choicest trees in the garden and sometimes upon the whole orchard. 

 You viewed them at night, the pride of the homestead, and, on your 

 next visit, the foliage was blackened and sickly and the young fruit 

 shriveled and worthless. Some said it was caused by electricity, 

 others by sunshine, others by insects, and so on, and just as 

 numerous were the remedies proposed ; as, for instance, digging in 

 iron filings about the tree, slitting the bark, painting the bark, etc., 

 all of which have been tried in vain. 



But now it has been shown conclusively that this terrible disease 

 is the result of a tiny bacterium, which lives in the sap and has the 

 power of locomotion. It is called by botanists Micrococcus 

 Affiylovonis, and its size, when magnified 890 diameters, is only 

 about half the size of a pin's head and very similar in shape. Prof. 

 ]. C. Arthur, who was at that time botanist of the Geneva Experi- 

 ment Station, in his report for 1887 described this bacterium and 

 stated that it was proved to be the real and only cause of the pear 

 blight. He discovered the organism itself in blighting tissue, and 

 inoculated healthy tissue of other trees with the germs from that 

 which was diseased, and, as a result, the healthy trees were at once 



