Natural Orders .] 
APPENDIX. 
571 
important circumstances; especially in the internal structure of its ovarium, 
and that of its pericarpium and seed ; but as in Olax there appears to be a 
double floral envelope, as its antheriferous stamina alternate with the seo-- 
ments of the inner envelope, and its ovarium does not cohere with either, 
there are sufficient grounds for regarding it, with Mirbel, as a distinct 
family. 
CASUARINEvE. The genus Casuarina is certainly not referable 
to any natural order of plants at present established ; and its structure 
being now tolerably understood, it may be considered a separate order, as 
Mirbel has already suggested.* 
The maximum ol Casuarina appears to exist in Terra Australis, 
where it forms one of the characteristic features of the vegetation. Thir- 
teen Australian species have already been observed, the greater number 
of these are found in the principal parallel, in every part of which they are 
almost equally abundant ; in Y r an Diemen’s Island the genus is less frequent, 
and within the tropic it is comparatively rare ; no species except Casuarina 
equisetifolia having been observed on the north coast of New Holland. 
Beyond Terra Australis only two species have been found, namely, C. equi- 
setifolia, which occurs on most of the intratropical Islands of the Southern 
Pacific, as well as in the Moluccas, and exists also on the continent of 
India ; and C. nodiflora, which is a native of New Caledonia. 
In the male flowers of all the species of Casuarina, I find an envelope 
of four valves, as Labillardiere has already observed in one species, which 
he has therefore named C. quad rival vis. f But as the two lateral valves 
of this envelope cover the others in the unexpanded state, and appear to 
belong to a distinct series, I am inclined to consider them as bractete. On 
this supposition, which, however, I do not advance with much confidence, 
the Perianthium would consist merely of the anterior and posterior valves, 
and these firmly cohering at their apices, are carried up by the anthera, as 
soon as the filament begins to be produced, while the lateral valves or brac- 
tcrn are persistent ; it follows from it also that there is no visible perian- 
thium in tlie female flower, and the remarkable ceconomy of its lateral 
bracteae may, perhaps, be considered as not only affording an additional 
t Plant, nov. hall. 2. p, 67. t. 218, 
* Annates du mus. 16. p. 451. 
