DAHLIA, a genus of large perennial herbaceous plants of the natural order composita, sub order corymbiferce, natives of Mexico. All the varieties in cultivation in our flower gardens, of which not fewer than 2,000 have been carefully enumerated, are derived tram two species, D. variabilis and D. coccinea, and chiefly from the former. Few plants, manifest so strong an inclination to sport and produce new varieties as the D., and florists have also obtained many by the artificial fecundation of one with the pollen of another. Dahlias were first brought to Madrid by Spanish botanists iu 1789, and were boon introduced into England, but did not become well-known in English flower-gardens till about 30 years after. The name was given in honor of Dahl, a Swedish botanist; but because another genus of plants had received the same name, an attempt was made to change it to Georgina, which is sometimes used on the continent, but D. universally prevails both popularly and among botanists in Britain. Among the most essential characteristics of a fine D., according to the estimation of florists, are a fullness of the
flower, a perfect regularity in the shape of the florets, and the absence of an eye or disk; and florets of the disk, as in other "double" corymbiferce, having assumed the appear ance of,florets of the ray. Dahlias have tuberous roots, which contain a considerable quantity of inulin (q.v.), and are in use as an article of food in Mexico. It was at one time attempted to introduce them into cultivation in Europe for the food either of man or of cattle; but the taste is nauseous to European palates, and even cattle do not readily eat them. Dahlias are often cut down in the northern parts of Britain by early frosts, in the very midst of their flowering; and their tubers require to be taken up for the winter, and stored in a dry place out of the reach of frost till spring. They are propa gated by seed, by cuttings, and by tubers. The finer varieties are sometimes grafted on more ordinary stocks.