TREMELLA, in botany, a genus of aquatic plants of a middle nature between the alga and conferva, being of a pellucid and membranaceous, and frequently gelatinous, nature. There are nine species; the most remarkable of which is the plicata undulata, or jelly rain tremella, found in pastures, and by the sides of gravel-walks in gardens after rains; not uncommon in spring, summer, and autumn. It is a membranaceous, pellucid, and gelatinous substance, without any visible root; of a yellowish dull green colour; assuming various forms, either round, angular, plaited or folded together irregularly, like the intestines or a pocket-handkerchief, an inch or two or more in diameter; soft to the touch when moist; but thin, membranaceous, and brittle, when dry; and of a black fuscous colour.—The ancient alchemists called this vegetable the flowers of heaven, and imagined that from it they would procure the universal menstruum; but all their researches ended in discovering that by distillation it yielded some phlegm, volatile salt, and empyreumatic oil. It has been extolled in wounds, ulcers, &c. but no regard is ever paid to it by judicious practitioners.