practical papers—fire blight . 
401 
this disease by assuming that it originated in the presence of 
fungoid germs, which break up the recently formed cells of wood 
growth, feed on their juices, and extend the disease with the cir¬ 
culation of the sap. 
He bases his theory upon being able to propagate the disease 
by innoculation of the spores of the fungus into sound wood. 
His remedy is to check the flow of sap and thereby retard the 
progress of the disease by presenting no new material to feed upon. 
Other well known horticulturists have adopted this theory, and 
more or less fully committed themselves to the cryptogamic or 
fungoid origin of fire blight, and have rested there, apparently re¬ 
signed to this inscrutable visitation, or content to direct their en- 
ergies to the discovery of some panacea for the obscure vegetable 
crypt. J. J. Thomas quaintly says, there are two remedies, one 
of which will never fail, “Cut away all affected parts as they 
appear; plant two trees for every one that dies.” 
A. J. Downing, in his original treatise upon the diseases of the 
pear, after describing the appearance and progress of this affection, 
attributes it to a diseased or poisoned circulation, which comes in 
•«& 
the following manner: A superabundant flow of sap in autumn 
is suddenly checked in its downward passage by frost, cells are 
ruptured, sap stagnates, decays in spring, becomes intermingled 
with ordinary sap in the alburnum and liber, which in the summer 
heat suddenly develop this disease. His preventive is to secure 
an early matured growth before the autumn frosts. (See Downing, 
10th ed,, page 324.) 
Dr. Warder devotes much space to this subject, (Am. Pomolo- 
gist p. 174); after discussing the “ parasitic fungi ” theory, he 
says, “a very important question has arisen, however, as to 
\ 
whether the inroads of fungi were the cause or the consequence only 
of disease. There is considerable testimony to favor the belief 
that in the potato, at least, we find with the appearance of the 
fungi, other causes of unhealthiness.” Dr. W. further says, “ this 
trouble is connected in many instances with an exceedingly vigor¬ 
ous growth of shoots, hence the inference of some, that if we can 
check this excessive vigor, we shall be able to prevent the occur¬ 
rence of this blight.” Dr. Warder and Dr. Hall have both given 
their testimony in favor of the value of “ root pruning,” as a pre- 
