26 MASSACHUSETTS HORTICULTURAL SOCIETY. 



Discussion. 



In reply to a question, Dr. Sturgis said that it was of great 

 importance that all fallen fruit, leaves, and other debris, should be 

 gathered up carefully and destroyed by fire, as all such collections 

 are almost sure to be stocked with spores of destructive fungi, 

 which if allowed to remain, would early in the following spring 

 be distributed by the winds, thus almost insuring the destruction 

 of a heavy percentage of the fruit that might set for that season's 

 crop. Even the most careful spraying of trees does not insure the 

 extinction of these germs. 



Dr. Sturgis replied to another question, that the Wild Cherry 

 trees have been a fruitful source from which has come the black- 

 knot fungus, so destructive of our cultivated plum and cherry 

 trees. He believed that as a preventive measure, all wild cherry 

 trees which show any evidence of the disease should be destroyed. 



Dr. Sturgis stated to another questioner, that the cracking by 

 frost of sap vessels in some hard-wooded trees, sometimes caused 

 an abnormal growth, closely resembling the black-knot of plum 

 trees, but that it was quite distinct from that disease in character. 



Apple-leaf rust ( Roestetia pirata ) is a fuugus produced from 

 spores, which have their origin in what are called Cedar-apples. 

 This latter was long considered a natural product of the Red 

 Cedar (Juniperus Virginiana), but investigation proved that it 

 was a fungus and had been named Gy^iinosporangium macropus. 

 Still later it was found to be only another form, or another 

 stage of growth of the same fungus as the Apple-rust (Rnistelia 

 jdrata), and that the spores of neither could be developed, except 

 upon the plant which produces the other form. Dr. Sturgis illus- 

 trated this by a case where an orchard was protected from wind 

 by red cedar trees. The fruit trees nearest the cedars were a 

 mass of leaf-rust every season, and the disease diminished as the 

 distance between the cedars and fruit trees increased. In that 

 case he recommended that the cedars be cut off from a belt one- 

 fourth of a mile wide, believing that would prove an effectual 

 remedy ; but where the 'wind had full sway it would carry these 

 red cedar fungus-sporidia for miles, and then they would be as 

 destructive as at nearer points. 



Whenever the foliage of sprayed trees is thereby injured it 

 shows that the mixture is too strong and needs further dilution 



