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 18 order, but of which the proper floral envelopes are reduced to a few irregularly placed scales.

Another Australian genus of Diosmeæ differs from the rest of the order in having a calyx with ten divisions, an equal number of petals, and an indefinite number of stamina with evidently perigynous insertion.

MYRTACEÆ. This is one of the most extensive tribes in Terra Australis, in which considerably above 200 species have already been observed, and where the order is also more strikingly modified than in any other part of the world. It is very generally spread over the whole of Australia, but its maximum appears to be in the principal parallel. Many observations might here with propriety be introduced on the more remarkable structnres which occur among the Australian Myrtaceæ; I must, however, 547] confine myself to a few remarks on the distribution of the most extensive genera.

Of Eucalyptus alone nearly 100 species have been already observed; most of these are trees, many of them of great and some of enormous dimensions. Eucalyptus globulus of Labillardière and another species peculiar to the south end of Van Diemen's Island, not unfrequently attain the height of 150 feet, with a girth near the base of from 25 to 40 feet. In the colony of Port Jackson there are also several species of great size, but none equal to those of Van Diemen's Island; and no very large trees of this genus were seen either on the south coast or in the equinoctial part of New Holland. Mr. Caley has observed within the limits of the colony of Port Jackson nearly 50 species of Eucalyptus, most of which are distinguished, and have proper names applied to them, by the native inhabitants, who, from differences in the colour, texture and scaling of the bark, and in the ramification and general appearance of these trees, more readily distinguish them than botanists have as yet been able to do. Eucalyptus, although so generally spread over the whole of Terra Australis, and so abundant as to form at least four fifths of its forests, is