soil will seldom suffer from blight of any kind. Too much 
trimming, too much moisture, and too rich soils are, in my 
opinion, some of the causes of blights in apple and pear 
trees. I believe there are several varieties of blights in 
apple trees and probably in pear trees also. I think I am in 
posession of facts and observations which will explode all 
the blight theories which I have seen published.” This gen- 
tleman certainly observed some of the conditions which may 
aggravate blight, but his was as far from the true cause as 
any of the blight theories he thought himself able to explode. 
FUNGI. 
The man who introduced the theory of a fungus origin 
of the disease was for a considerable time quite sate from 
contradiction. Many fungi are very small; to learn any- 
thing of them beyond the fact of their existence requires a 
microscope. They had then received little attention, little 
was known of them, and it was impossible to prove or dis- 
prove their casual connection with the disease. 
An investigator in 1872 ascribes the disease to a local 
fungus fermentation of the genus Torula and he observes 
that “Every condition that will prevent the bark and 
shoots from ripening will foster under high temperatures, 
in the presence of organic acid and vegetable nitrogenous 
matter, one or more species of Torulacei fungi.” And he 
further infers that contamination may come about by the 
absorption of the fungus germs by the roots, and in this case 
the fermentation proceeds from the sap-wood to the ex- 
terior. Drainage, or the removal of the tree to a more 
favorable place is recommended. The writer speaks of 
another form of the disease where the fermentation pro- 
ceeds from the surface to the interior. This he calls atmos- 
pheric blight. Now beyond the fact of the presence of 
fungi in the diseased tissues this was all theory. 
In 1875 Thomas Meehan, editor of the Gardener’s 
Monthly, in speaking of the researches of Dr. Hunt of 
Philadelphia, says he finds “That a very minute fungus 
germinates in the outer bark, enters the structure, destroy- 
ing the cells as it goes, till it reaches the alburnum, and 
then it penetrates clear to the pith, by the way of the med- 
ulary rays, totally destroying the branch from center to cir- 
cumference;” and he adds, “There is no other conclusion 
here than that arrived at by Dr. H., that in the true fire 
blight, fungi are the cause of the disease.” 
It was an easy matter to find fungi in the dead tissues 
* Department of Agriculture Report 1871, page 191. 
