Nature and Cause of the Potato Disease. 317 
ficence in the provision, for it renders that last change of 
matter which all organisms are doomed to undergo less hurtful 
to the living and more conducive to the purposes of vegetation. 
We have seen that the botriiis grows and fructifies with great 
rapidity, that it produces myriads of seeds, and that they are to 
be found in the earth. Now, if its office be to destroy the life of 
healthy vegetation, we may ask what has it done to support that 
character ? Has it ever destroved a single corn-field, devastated 
our fruit-trees, or ravaged our gardens ? Has it been known 
to bring forth its countless legions, and, like the deadly blast of 
the simoom, sweep all before it ? Has it, in short, ever robbed 
the earth of its green and beautiful covering, and converted 
it into a desert? Nature replies, no; and the experience of 
humanity responds to it. If, then, it has not acted generally, 
its attacks have been partial ; and if partial, particular ; and if 
particular, under certain conditions, that must have governed the 
act committed; and as particular action is opposed to general, 
so may we conclude the appearance of the botritis to be the effect 
of circumstances — a mere agent of the condition of things, and 
that its nature and habits unfit it to act generally. The other 
kinds of fungi observable in potatoes need not be noticed, as they 
are clearly referable to the state of matter in which they appear. 
It is not to be denied that ravages have been committed by insects, 
in some cases to an alarming extent ; but these, fatal as they may 
have been, have not the least connexion with our present subject 
in character, except as far as they may be traced to some peculiar 
state of the elements ; but although such cases are not identical 
in nature with fungi, they may nevertheless be usefully con- 
trasted with them as instances of ravages in the vegetable king- 
dom, and with that view 1 shall briefly mention a few. 
In June, 1830, a singular scene presented itself among the 
oaks in the weald of Kent. They were, from a state of luxuriant 
foliage, suddenly stripped of their leaves by the united attacks of 
myriads of caterpillars. Linnaeus states that the corn in the 
granaries of Sweden, for several years, was attacked by the 
Musca hordei, and that it sustained an annual loss of 100,000 
tons. Some years since the Hessian fly devastated the wheat- 
fiields of America ; and a species of locust, the Gryllus migra- 
torius from Tartary, laid waste a great part of Europe. Turnips 
suffer from the Haltica nemorum, or black jack; cherries from 
the Tephritis cerasis, or cherry-fly ; and the blossoms of the 
apple from a moth ; the bark of trees from the Tinea corticella 
and the Aphis lanigera; and other cases in which vegetation suffers 
from the depredations of insects might be named. Animals are 
not exempt from these attacks : thus oxen and cows suffer from 
the QSstrus hciemorrhoidalis, or bot, internally; sheep from the 
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