72 BULLETIN 380, U. 8. DEPARTMENT OF AGRICULTURE. 
ward by the advocates of the “weakened host” theory seems to be 
fully established; that is, that the chestnut trees have suffered se- 
verely in the southern Appalachian regions previous to the present 
epidemic, in some cases being practically exterminated, so that the 
range is now considerably less than formerly. The evidence on this 
point has been summarized by Clinton (18, pp. 408-413). Various 
writers quoted by him cite fire injury and borers and other insects 
as causes for this recession. 
Long (48, p. 8) considers a root rot due to Armillaria mellea as 
“very probably an important factor in the gradual recession of the 
chestnut” in North Carolina. It seems probable that all of the 
above-mentioned factors, and perhaps others, have played a part in 
the destruction of the chestnut in this region. 
RELATIVE SUSCEPTIBILITY OF SPECIES OF CASTANEA. 
The importance of Castanea dentata as a timber and nut tree and 
its abundance in eastern North America, where the blight is preva- 
lent, has made the chestnut blight an object of much investigation. 
Descriptions of the nature and importance of the disease, the rate 
of its spread, methods of distribution, and attempted methods of 
control have been given in detail by Anderson (1-5), Clinton (12-15), 
Heald (89-41), Metcalf (51 and 52), Metcalf and Collins (53), Ran- 
kin (62), and others. It may be sufficient here to state that the 
fungus enters the host through a wound in the bark, probably never 
or very rarely through lenticels or natural cracks, grows chiefly in 
the cambium, penetrating for only short distances into the wood, 
and kills the tree or branch by girdling. Once a tree is attacked, 
it is only a question of time till it succumbs. 
The chinquapin (Castanea pumila) was found by Murrill (58) in 
1908 to be attacked by Hndothia parasitica. Rogers and Gravatt 
(65) in 1915 made inoculations of Z'. parasitica on C. pumila and 
found that the parasite grew as rapidly on this host as on C. dentata. 
They attribute the apparent resistance of the chinquapin to its com- 
parative freedom from bark injury, a view also held by other writers. 
Pantanelli (60) and Metcalf (52) have proved that the European 
chestnut is readily susceptible to the disease. 
The only chestnuts thus far observed which show any resistance 
to Endothia parasitica are those of oriental origin. Metcalf (51) 
first pointed out the resistance of the Japanese chestnut. This 
observation has since been confirmed by Clinton (18, p. 375), who 
“failed to produce the disease in a Japanese variety in the [Conn.] 
station yard, although the bark was inoculated in 16 different places.” 
Van Fleet (84), in describing the spread of the chestnut blight in 
his breeding plats at Washington, D. C., says (p. 21): “The Asiatic 
chestnuts and the chinquapin-Asiatic hybrids are plainly highly 
resistant.” 
