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Class XXI. Morcecia. Order VI. Polvandria.

Gen. Char. Calyx generally five cleft. Corolla none. Stamens five to ten.

Spc. Char. Leaves oblong, glabrous, sinuate. Lobes rounded. Fruit oblong.

The Oak is a native of North America, a very valuable tree, and one of the largest of the forest; it frequently attains the height of - from seventy to one hundred feet; its trunk is covered with a thick bark of a dark brown colour. It flowers in April, and the fruit ripens in October. The acorns are round, flattened at the top, and placed in a saucer-shaped cup. It sends off numerous strong branches. The leaves are oblong, deeply sinuated, and form obtuse lobes; they are of a deep greenish colour. The flowers are small and yellow.

This extensive genus comprises not less than eighty species, of which not less than thirty or forty are found within the limits of the United States, and in many places comprise the largest portion of the timbered land, and is too well known to need further description.

Medical Properties and Uses. The Oak bark has long been esteemed as a powerful and useful astringent and tonic. It is highly recommended in obstinate cases of diarrhoea, and chronic forms of dysentery; also in leucorrhcea and other chronic serous discharges depending on debility and relaxation of the secreting vessels.

The decoction may also be employed with advantage as an injection, in cases of gleet, leucorrhcea, prolapsus, &c. Dr. Cullcn tells us that he has frequently employed the decoction with success in slight tumefactions of the mucous membrane of the fauces, and in many cases of prolapsus uvulae; and in a number of cases this decoction, early applied, has appeared useful in preventing these disorders. It must be remarked, however, that Dr. Cullen almost constantly added a portion of alum to these decoctions. An extract is procured from the bark by boiling down to a proper consistency, which is put up in small earthen pots.

Galls, which are so numerously found upon the leaves of this tree, are occasioned by a small insect, with four wings, called Cynips Querci Folii, which deposits an egg in the substance of the leaf, by making a small perforation through the under surface; the ball presently begins to grow, and the egg in the centre of it changes to a worm; this worm again changes to a nymph, and the nymph to the flying insect above mentioned, which by eating its passage out leaves a round hole; those galls which have no holes, are found to have the dead insect remaining in them.

Galls appear to be the most powerful of the vegetable astringents, striking a deep black when mixed with a solution of ferrum vitriolatum, and therefore preferred to every other substance for the purpose of making ink. As a medicine, they are to be considered as applicable to the same indications as the oak bark, and by possessing a greater degree of astringent and styptic power, seem to have an advantage over it, and to be better suited for external use. Reduced to powder, and made into an ointment, they have been found of great service in haemorrhoidal affections; their efficacy in intermittent fevers was tried by order of the Academy of Sciences; from their report it appears that the galls succeeded in many cases, and also that they failed in many others, which were afterwards cured by Peruvian bark.

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