of this secretion are in the Cinchona officinalis or Peruvian bark, Lambert Cinchona, t. 1, and every species, more or less, of Gentian.
Acid secretions are well known to be very general in plants. Formerly one uniform vegetable or acetous acid was supposed common to all plants, but the refinements of modern chemistry have detected in some a peculiar kind, as the Oxalic acid, obtained from Oxalis or Wood Sorrel, and several others. The astringent principle should seem to be a sort of acid, of which there are many different forms or kinds, and among them the tanning principle of the Oak, Willow, &c.
On the other hand, two kinds of Alkali are furnished by vegetables, of which the most general is the Vegetable Alkali, properly so called, known by the name of Salt of Tartar, or Salt of Wormwood, or more correctly by the Arabic term Kali. The Fossil Alkali, or Soda, is most remarkable in certain succulent plants that grow near the sea, belonging to the genera Chenopodium, Salsola, &c. When these plants are cultivated in a common soil, they secrete Soda as copi-
