46 Forest Club Annual 





winter of 1903-04, aggravated by droughts, especially that of 1907, 

 materially reduced the vitality of the chestnuts allowing the fun- 

 gus to rise as a virulent parasite. Metcalf (11) was of the opin- 

 ion that the fungus was imported from the Orient with the Japan- 

 ese chestnut. Chestnut bark and branches were recently received 

 from China bearing a disease which is shown by Shear and Stev- 

 ens ( 18) to be identical with the American chestnut bark disease 

 morphologically and physiologically, indicating that the disease 

 is indigenous to China. 



When the disease was discovered in 1904 the center of in- 

 fection was in western Long Island. Two years later the same 

 disease was found to exist in New Jersey, Maryland and Vir- 

 ginia. Four years later it .was reported from Connecticut and 

 Massachusetts. It is now known to occur from Maine to west- 

 ern Pennsylvania, Virginia, and West Virginia, and has recently 

 been reported from British Columbia (6). Unless some effective 

 method of control is discovered in the near future the disease will 

 probably destroy the extensive chestnut forests of the South. 

 This disease must, therefore, be seriously considered in formulat- 

 ing a forest policy for many of our Eastern forests. However, 

 since Tourney (19) and Richards (15) have recently discussed 

 the silvicultural treatment of the chestnut, no further comment 

 on this phase will be made in this paper. 



MORPHOLOGY, PHYSIOLOGY, AND ECOLOGY. 

 Development of Canker. 



When the spores of this fungus enter the trunk or branches 

 of a chestnut tree a lesion is produced. Cankers develop within 

 from two to four weeks from the time of inoculation. The mycel- 

 ium spreads in all directions from the center of infection, giving 

 rise to concentric rings, which mark successive periods in the 

 growth of the canker. It was found that during an optimum 

 growing period the rate of growth of the canker averaged about 

 3.5 cm. in diameter per month under field conditions. A tree, in 

 the greenhouse at the University of Pennsylvania twenty days 

 after inoculation, had developed a canker 10.2 cm. in diameter, 

 giving an average rate of growth of about .5 cm. per day from 

 the time of inoculation. The point of inoculation was kept moist 

 with wet cotton and the humidity of the greenhouse was relatively 

 high. This is considered maximum growth because of the un- 

 usually favorable conditions for the development of the fungus. 



