PRACTICAL PAPERS—FIRE Plight. 
399 
first approach of the disease by a change of color of some one or 
more leaf stems, or of sections of young wood, which rapidly ex¬ 
tends until the cause is removed, or the branch partially or wholly 
dies. Sometimes only patches of blight appear, of small dimen¬ 
sions, which do not seriously affect the health of the tree more 
than the removal of so much of the bark. Of the first appearance 
of this malady, I have no certain information, but find in the old¬ 
est farm and garden journals extant, much the same description 
and complaint of its appearance at irregular intervals, as now, but 
more generally charged to some supernatural or lunar agencies. 
The oldest account we have of this disease is that of Duhamel 
in 1768. 
The locality of this affection is a point of especial interest. It 
is known and recognized in the old world, but they experience so 
little of its ravages, that they have passed it almost unnoticed. 
The even and general low temperature of western Europe evi¬ 
dently is not favorable to its development, and it is reserved as a 
“thorn in the flesh ” for our extremely changeful climate and rich 
soils, and, more than all, to the dark alluvials and humid heats of 
the Mississippi valley. 
The testimony of numerous correspondents in the west confirms- 
my own observation, that in close , sheltered locations and excessively 
rich soils , this disease is much more prevalent than upon the more 
bleak and barren highlands, and is especially prevalent during 
and succeeding a period of sultry, moist atmosphere. It prevails 
most frequently when the conditions are favorable to excessive 
growth. 
I will now refer to some of the many theories advanced upon 
the cause of this affection, with observations and remarks of some 
of our most careful and scientific horticulturists. The theory of a 
purely electrical cause has prevailed largely among those who wit¬ 
ness results, “as if a stroke of lightning had touched the tree,” 
but is shown very diverse from the known laws of electrical 
phenomena. The same may be said of the “hot air” theory. 
More plausible is the “insect theory;” and some, after finding 
occasionally minute grub in the part affected, rest upon this 
“insect theory” as the cause of a disease a thousand fold more 
widespread than the presence of a comparatively harmless insect. 
