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30 in the more essential parts of fructification, and even in their remarkable involucella. Of this genus, one species has a compound umbel of four many-flowered radii; a second has an umbel of three rays with two or three flowers in each; several others, still retaining the compound umbel, which is proved by the presence of their involucella, have from four to two single-flowered rays: and lastly one species has been observed, which is reduced to a single flower; this flower, however, is in fact the remaining solitary ray of a compound umbel, as is indicated by the two bracteæ on its footstalk, of which the lower represents the corresponding leaf of the general involucrum, while the upper is evidently similar to the involucellum of the two-rayed species of the genus.

558] COMPOSITÆ. Of this family, which is the most extensive among Dicotyledones, upwards of 2500 species have been already described. About 300 are at present known in Terra Australis, in which therefore the proportion of Compositæ to its Dicotyledonous plants is considerably smaller than that of the whole order to Dicotyledones generally, and scarcely half that which exists in the Flora of South Africa. It is also inferior in number of species to Leguminosæ, like which it seems expedient to consider it as a class including several natural orders. Of these orders Cichoraceæ and Cinarocephalæ are comparatively very rare in Terra Australis, not more than ten species of both having hitherto been observed.

The class therefore chiefly consists of Corymbiferæ, which are very generally diffused; they are however evidently less numerous within the tropic, and their maximum appears to exist in Van Diemen's Island. Corymbiferæ may be subdivided into sections and the greater part of the genera peculiar to Terra Australis belong to that section which may be named Gnaphaloideæ, and exist either in the principal parallel or higher latitudes.

The whole of Compositæ agree in two remarkable points