390 CONNECTICUT EXPERIMENT STATION REPORT, IQI2. 
healthy one. * * *° Dry weather checks the disease by sup- 
pressing spore production. * * * Winter injury is not common 
over the whole range of the bark disease, but may be locally 
important in producing : lesions through which the’ parasite 
enters. -Winter injury bears no other relation to the bark 
disease.” Metcalf (35, p. 225) in 1912 said again: “No definite 
evidence, experimental or otherwise, has: been adduced: to show 
that a tree with reduced vitality is more susceptible to infec- 
tion,.or:that the disease spreads more rapidly in such: a tree 
than in a perfectly healthy and well nourished tree of ‘either 
seedling or coppice growth, provided that such reduced vitality 
does not result in or is: not accompanied by bark injury by 
which spores may gain entrance.” 
Now, if the condition of the host bears no relation to the 
rise and spread of the disease, the writer knows of no satis- 
factory explanation for its sudden and destructive appearance 
in this country except its importation from some foreign 
country. The evidence to date, however, is very strongly 
against the idea that it is an imported pest, as we shall show 
later. Among the farmers in Connecticut who have been able 
to watch this disease rather closely there are many who believe 
that the weakened vitality of the chestnuts has had considerable 
to do with its development and spread in this state. The 
writer more than anyone else has advocated this view, and we 
propose to give here the reasons we have for holding it. 
Briefly expressed, they are as follows: 
The chestnut blight was brought to sudden prominence just 
after the severe winter of 1903-04, which injured and killed 
fruit and forest trees in general along the coast and water- 
courses, of which New York City was the central point. The 
resulting enfeebled condition of the chestnut enabled the blight, 
a previously inconspicuous parasite, to spring into sudden 
prominence on these trees and to gain credit for the death of 
others which had been largely or entirely due to winter injury. 
Since then we have had one or two severe winters, and more 
especially several dry summers, that have injured not only the 
chestnut, but other forest trees over an extended area. Due 
to its successful attack on the weakened trees, the blight fungus 
has perhaps acquired an added virulence that has enabled it to 
attack apparently healthy trees, especially those of sprout 
