own, and other parts of Europe, have been varied, and even the quantity of rain that falls, been lessened by 
the felling of woods and clearing extensive tracts of forest land, are truths too well known to be more than 
just adverted to. The influence exerted by plants in the conversion of inorganic into organic matter, is 
likewise another most important function, and one exclusively their own, for it is a power that animals do 
not possess ; while the metamorphoses they effect in refuse matter, changing every sort of filth and ordure 
which is supplied to them in the form of manure, into substances fit for food or raiment, are no less strange 
than they are common. We are astonished at the chemist, and extol his skill for converting, by an ex- 
pensive process, linen into sugar, wood into a sort of flour, starch into gum, and so forth — and rightly do we 
give way to wonder ; but conversions similar, though much more perfect and extensive, are being wrought 
by every plant, even by the humblest weed that grows. They are constantly engaged in the manufacture, if we 
may so express ourselves, of flour, sugar, oil, resin, flax, cotton, and all the other numerous vegetable substances 
which are so conducive to our comfort, nay, so essential to our existence, from earth, air, and water — pre- 
senting us not only with new organic matter, derived by their agency from the mineral kingdom, but also 
renovating that which, having been fed on or otherwise used and spoiled by men and animals, they cast, 
with loathing on the dunghill, and for the most part fail to recognise when returned to them as corn, and 
oil, as culinary vegetables, as delicious fruit, and as fragrant and beauteous flowers. The scientific culture 
of plants is founded on a knowledge of their structure and their functions, or it is a branch of vegetable 
physiology ; and vast have been the improvements in both horticulture and agriculture since empirical 
practise has in some measure been superseded by scientific principles. The system of assolements, or the 
rotation of crops, by which the produce of our land has been quadrupled and the acclimation of plants 
with their hybridizations, by which the fruits and flowers of more southern regions are reconciled to our 
climate, are a few among the many examples which might be given of the benefits conferred by this science 
upon some of the most useful arts. The increase of food, and the fact of the more choice vegetables be- I 
coming cheap and common, cannot fail to be observed by every one. Each year our markets and shops j 
are supplied more abundantly and with more choice vegetables. Sea kale, for example, which a few years j 
since was rare and costly, is now cheap and common. Coleworts, cauliflowers, and the various kinds . of 
brocoli, are not only improved, but have become more plentiful and cheap ; while the potato, second only 
to corn in its importance, if not altogether as an esculent vegetable, the offspring of science, has been so 
much improved, varied, and multiplied by human skill and industry, and so much increased in value, as to | 
be more indebted to its foster parents in Europe, than to the American savages by whom it was originally i 
discovered. But here inexorable time cuts short the thread of our discourse. 
If plants in a state of health are so essential to our existence, and conduce so much to our comfort and 
our pleasure, it would surely be ungrateful in us to neglect them when diseased. Vegetable pathology 
forms, then, another subordinate branch of our science; and although the maladies of plants have not j 
hitherto been studied so much and so successfully as those of men and animals, still we know enough of 
them to be able to perceive that they suffer from the attacks of various diseases, some of which we | 
are enabled to relieve, and others which are incurable in the present state of our knowledge. Plants, 
perhaps, suffer more from invermination and the attacks of insects than from any other means; yet they j 
are subject to other diseases, both of sporadic and epidemic kind. Some of these even bear a similitude to i 
animal disorders, and have therefore, received similar names, of which Wildenow furnishes a catalogue. 
Thus, plants are affected with atrophy, tabes or consumption, anasarca or dropsy, haemorrhage, lepra, verrucse, 
or warts, chlorosis, icterus, ulcerations, common gangrene, and necrosis, or dry gangrene, besides various 
kinds of deformities, wounds, mutilations, &c, &c. They are likewise subject, especially the cacti, to a j 
peculiar kind of sudden death, called by the French “la mort/’ by which, when affected, a branch or even a 
whole plant is as rapidly destroyed as the use of a limb is lost, or death produced in animals by apoplexy. 
The diseases of plants are often, although injurious to them, beneficial to man, while at other times 
their unhealthy conditions so far deprave and change the quality of their ordinary productions, as to render 
those which are usually wholesome and nutritious, either worthless, baneful, or even poisonous. The pro- i 
duction of agallocum and the various kinds of galls and gums, are instances of vegetable disorders being j 
serviceable to man, while the diseases of corn, such as the smut, canker, rust, &c., and especially the ergot, 
are familiar examples of the fearful havoc they make in our crops, the former rendering a harvest worthless, | 
and the other converting our sustaining corn to poison. It must, however, be recollected that the ergot is j 
when properly administered, a most valuable medicine, and also that these apparently grievous evils are I 
such only on a partial view; they are injuries only when particular instances are selected and isolated, for j 
it is on all hands confessed that in the general economy of nature they are highly beneficial, as forming a 
part of the system of checks and counterchecks by which the balance is corrected when the strong over- 
power and would exterminate the weak, and preserve that quality which could not be otherwise maintained, 
to modify their influence, and protect ourselves from the injurious prevalence, is the duty of science, and 
the more the study of vegetable pathology is pursued, the greater will be the power we shall obtain of turning 
even these apparently malevolent incidents to our advantage.” 
