Natural Orders .] 
APPENDIX. 
569 
define this natural order, one of whose most remarkable characters consists 
in its unilocular ovarium, containing more than one, but always a deter- 
minate number of ovula, which are pendulous and attached to the apex 
of a central receptacle. This receptacle, which varies in its figure, in 
the different genera, in some being filiform, in others nearly filling the 
cavity of the ovarium, had not been previously noticed in any plant of the 
order. 
The greater part of the Santalacese of Terra Australis are found in 
the principal parallel, to which several genera, namely, Leptomeria, 
Corethrum, and Fusanus are nearly limited : Santalum on the other hand is 
found chiefly within the tropic. 
I have added Exocarpus and Anthoholus to this order, with certain 
genera of which they agree in habit and many points of structure, both of 
the flower and fruit : but they are readily distinguishable from the whole 
order by their fructus superus, and they may possibly differ also in the 
internal structure of their ovarium, which has not yet been satisfactorily 
ascertained. 
The genus Exocarpus is most abundant in the principal parallel and 
southern parts of Terra Australis, but it is not unfrequent even within the 
tropic. Exocarpus cupressiformis is not only the most common species 
of the genus, but the most general tree in Terra Australis, being found in 
nearly the whole of the principal parallel, in every part of Van Diemen’s 
Island that has been visited, and even within the tropic. I am acquainted 
with only three plants that have in that country an equally extensive range. 
These are Anthistiria australis, the most valuable grass as well as the 
most general plant in Terra Australis ; Arundo Phragmitis, less frequent 
than the former, but which extends from the southern extremity of Van 
Diemen’s Island to the North coast of New Holland ; and Mesemhryan- 
themum cequilaterale, which occurs on almost every part ot the sandy sea 
shores, of both these Islands. 
Exocarpus is not absolutely confined to Terra Australis, for Mr. Bauer 
has discovered a very remarkable species bearing its flowers on the margins 
of dilated foliaceous branches, analogous to those of Xylophylla ; and 
Xylophylla longifolia, which was taken up by Linneus from Rumphius,* 
* Xylophyllos ceramica, Herb. amb. 7 ■ P- 19- 1. 12. 
4 D 
VOL. II. 
