shoots and even their older branches die away 
toward the extremity, that it has been regarded 
by some close observers as the sole cause of their 
canker; a kind of fungus totally different from 
this accompanies, and has been thought by some 
persons to rouse, precisely similar symptoms 
of canker in apple-trees; and minute fungi of 
| various kinds, particularly of the genera clado- 
sporium, antennaria, and helminthosporium, in- 
variably accompany canker in the larch - trees, 
and are sometimes so prodigiously abundant as 
to give the trees the appearance of being coated 
with soot. But two of the most distinguished 
fungologists in Britain, after closely examining 
specimens of cankered larch, expressed a decided 
opinion that the presence of the fungi was not 
the cause but a consequence of the disease, and 
was probably occasioned by the exudation of tur- 
pentine; and one of the two—Sir W. J. Hooker 
—remarked, “Diseased trees exuding moisture, 
or even in moist seasons, instead of having a 
clean bark or foliage, are very liable to the at- 
tacks of various fungi; but, nevertheless, they 
do not seem to afford a proper humus to bring 
them to a state of perfection. I have often ob- 
served this to arise again from a bad, and espe- 
cially cold and wet, state of the soil.” 
The opinion that canker is occasioned by the 
weakness of a tree’s constitution, by a distemper 
in all its juices, or by a deficiency in its func- 
tional energies, and by a consequent inability to 
imbibe and elaborate sufficient nourishment for 
existing organs, and sufficient matter for the 
formation of new parts,—this opinion makes 
very ample allowance for the malign influence 
of bad climate, bad soil, bad cultivation, bad va- 
| riety of tree, and all sorts of accidents and unfa- 
vourable circumstances; and, as maintained by 
|| Some writers, it even seems to speak of constitu- 
tional distemper as a convenient general ex- 
pression for the operation of all kinds of con- 
ceivable causes. G. W. Johnson, Hsq., who is a 
strenuous advocate of this opinion, enumerates 
and illustrates most of the causes which are usu- 
ally alleged, and then says, “All these facts unite 
in assuring us, that the canker arises from the 
tree’s weakness. It matters not whether its 
energy is broken down by an unnatural rapidity 
of growth, by a disproportioned excess of branch- 
es over the mass of roots, by old age, or by the 
disorganization of the roots in an ungenial soil; 
they render the tree incapable of extracting suf- 
ficient nourishment from the soil, consequently 
incapable of developing a sufficient foliage, and 
therefore unable to digest and elaborate even 
the scanty sap that is supplied to them.” 
Both soil and subsoil, in spite of the assertion 
of a few writers to the contrary, appear to exert 
a very considerable influence. A wet retentive 
subsoil does not permit sufficient aeration, can- 
not perform sufficient digestion, and will not 
allow a sufficient supply of perfectly fresh ele- 
i of healthy sap; and therefore must act 
eee 
= —- 
CANKER. 
malignly, not alone as a reservoir of cankering 
vapours, but as an originator of impoverishing 
and poisonous juices. A deep and very rich soil 
gives trees a plethoric and dropsical habit, and, | 
in consequence, occasions so powerful a predis- | 
position to canker, that a cure for this disease in | 
an orchard has sometimes been found in the sim- 
ple process of wheeling away one stratum of the 
soil, and diluting the remaining stratum. If | 
a subsoil either be ill-drained or consist of fer- | 
ruginous gravel, or if a soil be clayey and not 
kept well-drained and porous, all trees which 
grow upon it, but especially fruit-trees, are ex- 
ceedingly liable to become cankered. A soil 
exhausted by long cropping, or charged with the 
sporidia of accumulated growths of minute epi- 
phytic fungi, is peculiarly unfavourable; and 
hence an old worn-out orchard, if replanted with | 
fruit-trees, is almost certain to communicate 
canker to even the most vigorous young plants 
which can be selected. A cold situation, fre- 
quency of raw fogs, and the vernal prevalence 
of piercing and moist east winds, seem to be the | 
principal cankering elements in climate. Inju- 
dicious pruning, bruises, damage to the bark, 
and all similar accidents, if they do not originate 
canker, seldom fail to aggravate it. The young- 
est and most vigorous larch-trees appear to be 
more subject to canker than the older and less 
vigorous ; yet, with this exception, the oldest 
trees of any species growing in one group, or in 
one set of circumstances, whether they be tim- | 
ber-trees or fruit-trees, are more frequently at- 
tacked than the younger. Trees of every age | 
are liable to canker; but, as a general rule, all 
become increasingly liable as they advance in 
age, and particularly such as have had a vigor- | 
ous growth in their youth. All grafting varie- 
ties of fruit-trees, also, become more and more 
cankerable as they multiply in reproduction, till | 
they eventually acquire such an accumulation | 
of peccant humour as to be continually diseased, 
and no longer propagable. The scions of an old 
variety of fruit-tree merely multiply an aged in- | 
dividual ; and though they acquire temporary 
vigour from the young and stimulating sap of 
the stocks on which they are grafted, they be- 
come, in a few years, as cankerable and decrepid 
as the parent tree. The golden pippin, the old- 
est variety of the apple-tree at present cultivated, 
is more frequently and severely attacked by can- 
ker than any other variety. “Ido not mean to 
assert,” says Mr. Knight, “that there ever was a 
time when an apple-tree did not canker on un- 
favourable soils, or that highly cultivated varie- | 
ties were not more generally subject to the dis- 
ease than others, where the soil did not suit 
them. But I assert, from my own experience 
and observation within the last twenty years, 
that this disease becomes progressively more fa- 
tal to each variety as the age of that variety, 
beyond a certain period, increases; that all the 
varieties of the apple which I have found in the 
Nee ee eee eee 
