have been observed, of whichi the greater part are referable to Boronia, Correa, Eriostemon, and Zieria, of Dr. Smith, and Phebalium of Ventenat. Of these genera Boronia is both the most extensive and the most widely diffused, existing within the tropic, and extending to the South end of Van Diemen's Island; like the others, however, its maximum is in the principal parallel, at both extremities of which it is equally abundant. Correa, though extending to the south end of Van Diemen's Island, is not found within the tropic, nor was it observed at the western extremity of the principal parallel; in the intermediate part of which, however, where many of the peculiarities in the [545 vegetation of the parallel are less remarkable, or entirely wanting, it may be said to abound.
Eriostemon, which appears to be most abundant at the eastern extremity of the principal parallel, has not been observed either at its western extremity or intermediate part; it extends, however, to the south end of Van Diemen's Island on the one hand, and within the tropic as far as Endeavour River on the other.
Phebalium, very nearly related to Eriostemon, has like that genus its maximum at the eastern extremity of the principal parallel, it is found also at the western extremity of this parallel, and as far as the south end of Van Diemen's Island, but it has not been observed within the tropic.
Zieria seems to be limited to the eastern extremity of the principal parallel, and the more southern regions.
The most remarkable plant of the order with regard to structure, is that imperfectly figured and described in Dampier's voyage.[1] Of this genus, which may be named Diplolæna, I have examined Dampier's original specimen in the Sherardian Herbarium at Oxford, and others recently collected, also at Shark's Bay, in the voyage of Captain Baudin, and have ascertained that what appear to be calyx and corolla in this singular plant, are in fact a double involucrum containing many decandrous flowers, whose stamina and pistilla exactly agree with those of the
