88 



This disease, lor which the fungus Endothia parasitica, brought 

 into this country from .Asia many years ago, is mainly responsible, 

 has now practically destroyed the valuable stands of chestnut tim- 

 ber which formerly flourished in the forests of the eastern C S. 

 We are attempting to solve this problem by the method of plant 

 breeding. 



I he Japanese and Chinese species of chestnut, Castanea crenata 

 and ( . mollissima, respectively show considerable resistance to the 

 attacks ot the fungus which induces the blight. Unfortunately 

 these are species ol comparatively low stature, so that they can 

 never he used as substitutes for the American chestnut, Castanea 

 dentata, in reforestation programs, if a stand of tall timber is to 

 he the ultimate objective. 



In 1930 we began breeding the Japanese and American species 

 together with the object ot developing a tree which should inherit 

 the tall-growing character of the American parent plus the re- 

 sistance of the Japanese parent ( Fig. 4). Finding, later, that the 

 Chinese chestnut was still more disease-resistant than the |apanese, 

 we began crossing the American species with this. also, in l l ->35. 



Summary ot results to date: 



1. We have found thai the Japanese-American hybrids are only 

 a little more disease-resistant than their American parents. 



2. However, most of these Japanese-American hybrids resemble 

 the American parent in their upright habit and show a rate of 

 growth much exceeding that of the American. 



3. Beginning in 1937, we have made a large number of crosses 

 ot these Japanese-Americans with disease-resistant Chinese indi- 

 viduals. These hybrids may show greater resistance than the |ap- 

 anese- Americans, hut they are still too young for us to make any 

 definite statement. 



4. We have a large number (about 150) of hybrids resulting 

 from the interbreeding ol Japanese-American hybrids. Some of 

 these may eventually give the desired result. 



5. We have acquired a living collection of all species of Cas- 

 tanea that are known to grow in the world, with the exception of 

 three Asiatic chinquapins. 



6. By an inoculation method we have learned the degree of sus- 

 ceptibility ol these different species. 



