Botanical Division 



CRYPTOGAMIC BOTANY AND PLANT PATHOLOGY. 



(EDEMA OF APPLE TREES. 



During the month of July specimens of diseased apple twigs were 

 received from Mr. E. A. Crow, of New York city. The soft outer 

 tissue of the limbs was in a state of decay and occupied by a fungus, 

 some species of Fasarium, which resembled F. arcuatum B. & C, 

 which was described from the bark of Pirus mains in South Carolina. 

 Mr. Crow had supposed this fungus to be the cause of the trouble, and 

 had tried the use of the Bordeaux mixture after having scraped off the 

 bark from the diseased places. Since so many of the species of the 

 genus Fusariutn grow only in tissues wliich have been injured by some 

 other agent, and all of the material which was first received was in 

 such an advanced state of decay, I requested Mr. Crow to send me 

 Bome fresh specimens which would represent the entire progress of the 

 trouble from its inception. From this material, which was received in 

 good condition, the external peculiarities of the disease may be 

 described as follows: 



Minute elevations appear on the surface of the branches or trunks, 

 which gradually increase in size from one-eighth to one-fourth of an 

 inch long and nearly as wide. They are usually quite close together 

 and frequently by increase in size, become confluent when a large num- 

 ber extend over quite a large surface and appear as one of very irregu- 

 lar form. These elevations present the appearance of blisters, and 

 they are well shown in figure 1, which is from a photograph of three 

 of the specimens received. Two of them show the appearance of the 

 twigs when the blisters are most prominent, while one of them shows 

 the collapsed condition of the tissues which always results after the 

 tissues are broken down from decay. 



Microscopic sections through the parts of the twigs where the 

 trouble is recent, shows that no fungus is present, and in fact there is 

 no ground for the casual connection of any parasitic organism. Imme- 

 diately beneath the periderm the young phellogen tissues at the points 

 of the blisters is seen to be very greatly elongated radially. This 



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