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 Rh hardly found beyond this country. I am acquainted with one exception only, in an additional species which is said to be a native of Amboyna.

Next to Eucalyptus in number, is the beautiful genus Melaleuca, of which upwards of 30 Australian species have already been observed, exclusive of Tristania, Calothamnus, Beaufortia, and an unpublished genus which I separate from it. The maximum of Melaleuca exists in the principal parallel, but it declines less towards the south than within the tropic, where its species are chiefly of that section which gradually passes into Callistemon, a genus formed of those species of Metrosideros that have inflorescence similar to that of Melaleuca, and distinct elongated filaments. With the exception of two species of this section, namely, Melaleuca leucadendron, and M. Cajeputi, the genus Melaleuca appears to be confined to Terra Australis.

Leptospermum, of which, nearly 30 Australian species have been observed, exists also in New Zealand and in the Moluccas. In Terra Australis its maximum is decidedly in the principal parallel, and like Melaleuca, it is much more abundant in the southern regions than within the tropic.

Bæckia, to which I refer Imbricaria of Dr. Smith, as [548 well as the opposite-leaved Leptospermums, is also an extensive Australian genus, having its maximum in the principal parallel, extending like the two former genera to the highest southern latitude, and hardly existing within the tropic: one species, however, has been found in New Caledonia, and that from which the genus was formed is a native of China.

COMBRETACEÆ. I have formerly made some