Limited in number as the new species really are, they will nevertheless constitute, when added to the discoveries recently made, through the medium of expeditions to the interior, from the colony of Port Jackson, very important materials to carry on that Flora of Australia, so very ably commenced by Mr. Brown. Since that eminent botanist has already advanced much important matter in the valuable essay, published at the close of the account of Captain Flinders' voyage, respecting the relative proportions of the three grand divisions of plants in Australia, as far as they had been discovered at that period, and has, from very extensive materials, given us a comparative view of that portion of its Flora, and the vegetation of other countries; I shall now simply submit a few general remarks in this notice, on certain plants of established natural families, that have been discovered in the progress of these voyages; closing this paper with some observations, chiefly illustrative of the geographical diffusion of several Australian plants known to authors, whose localities have hitherto been exceedingly limited.
PALMAE. On considering the vast expanse of the continent of Terra Australis, and that great extent of coast which passes through climates favourable for the production of certain genera of this remarkable natural family, it is singular that so few of the order should have been discovered: a fact in the history of the Australian vegetation, which (upon contemplating the natural economy of many other genera of plants) can only be considered as accounted for, by the great tendency to drought of at least three-fifths of its shores.
To Corypha, Seaforthia, and Livistona, the only three genera that have been enumerated in the productions of the Australian Flora, may now be added Calamus; of which a species (discovered without fructification, by Sir Joseph Banks, during the celebrated voyage of Captain Cook) has at length been detected bearing fruit in the vicinity of Endeavour River. The existence of this palm, or rattan, on the East Coast, to which it is confined, seems almost to be limited to an area within the parallels of 15 and 17 degrees South; should, however, its range be more extensive, it is southerly one or two degrees, in which direction a remarkable primary granitic formation of the coast continues, throughout the whole neighbourhood of which is a peculiar density of dark moist forest, seemingly dependent on it, and evidently indispensable to the life of this species of Calamus; but at the termination of this geological structure, it most probably ceases to exist. A dioecious palm of low stature, and in habit similar to Seaforthia, was detected in the shaded forests investing the River Hastings, in latitude 31 degrees South, bearing male flowers; but as it may prove to be a dwarf state of a species of that genus, which has lately been observed, with all its tropical habits, in a higher latitude, it cannot now be recognised as a sixth individual of the family whose fructification has been seen.
Although this order has been observed to be sparingly scattered along the line of East Coast almost to the thirty-fifth degree of south latitude, its range on the opposite shores of the continent is very limited. Upon the North-west Coast, the genus Livistona alone has been remarked, in about latitude 15 degrees South; beyond which, throughout a very extensive line of depressed shore, towards the North-west Cape, no palms were seen. If the structure of a coast, and its natural disposition to produce either humidity or drought be consulted (a point, with respect to this order, as well as certain other tropical tribes, appearing very important) those portions of the western shores recently seen, indicate no one character that would justify the supposition of the existence of the Palmae in the corresponding extremes of the respective parallels that produce them on the opposite or East Coast. Another remark relative to the economy of this family is, that in New Holland it seems confined to the coasts, Corypha australis, so frequent in particular shaded situations in the neighbourhood of Port Jackson, having never been detected in the vicinity of, or upon the mountains, much less in the distant country to the westward of that extensive boundary.
ASPHODELEAE. Among the several described plants in the Herbarium, referred to this family, that were collected upon the East and South-west Coasts, are specimens in complete fructification of a remarkable plant of arborescent growth, having a caudex twenty feet high, and all the habits of Dracaena. It probably constitutes a new genus distinct from Cordyline of Commerson, to which, however, it appears closely allied; and has an extensive range on the East Coast, where, although it has for the most part been observed within the tropic, it extends nevertheless as far as latitude 31 degrees South. The only plants of Asphodeleae remarked on the north-western shores, were an imperfect Tricoryne, probably Tenella of Mr. Brown, discovered by that gentleman during the Investigator's voyage on the South Coast; and the intratropical Asparagus, which is frequent in latitude fifteen degrees South.
CONIFERAE. To the general observations already made on that part of Coniferae inhabiting the southern hemisphere, may be added some important facts, to be gathered from the plants in the Herbarium of the late voyages, that will afford a very correct view of the fructification of some doubtful genera, as well as their limits. Among these the fruit of Podocarpus aspleniifolia of M. Labillardiere, was observed, together with the female fructification of another tree (the Huon pine) found also at the southern extremes and western coast of Van Diemen's Land, which may prove to be a Dacrydium. Callitris, of which seven species are known, and principally found in the parallel of Port Jackson, has also been discovered upon the North-west Coast, in about latitude 15 degrees South; and another species, remarkable for its general robust habit, was observed at Rottnest Island, on the West Coast. A tree, most certainly of this family, and probably (from habit) a Podocarpus, has been seen upon the East Coast, within the tropic, but the absence of fructification prevented its genus being satisfactorily determined. With respect to the extent of the order in the Islands of New Zealand, some recent specimens gathered upon the northern, prove one of its pines to be a Podocarpus; and another, producing a cone, and solitary, alternate scattered elliptical leaves, shows its relation to Agathis of Salisbury, or Dammar pine of Amboina.
URTICEAE, whose mass appears also to be confined to equinoctial countries, may be considered very limited in those parts of Terra Australis lying within the tropic recently explored. Ficus is the most considerable genus of the order in that continent; and although chiefly found on the north and north-western shores, is also traced on the East Coast, almost to latitude 36 degrees South, where the trees attain an enormous size. About sixteen species are preserved in the collections of the late voyages; all small trees, and one half of which has been gathered on the North-west Coast.
A species of Morus, bearing small white fruit, was discovered upon the continent and islands of New South Wales within the tropic, where also a new genus of the order, with radiated leaves, has been traced as far as Endeavour River. Of the genus Urtica, whose numerous species can simply be considered as of herbaceous duration, although a few of tropical existence assume a fruticose habit, there is one plant in the vicinity of the Colony of Port Jackson, remarkable for its gigantic, arborescent growth; many specimens having been remarked from fifteen to twenty feet in height, of proportional robust habit, and of highly stimulating nature.
SANTALACEAE. Nearly three-fourths of the Australian portion of the order described, were formerly discovered in the parallel of Port Jackson, upon the shores of the South Coast, and in Van Diemen's Land. The genus Choretrum, however, heretofore limited to the southern extremes of the continent, approaches within about two degrees of the tropic on the West Coast, having been lately observed on Dirk Hartog's Island. It is rather remarkable that neither Leptomeria nor Choretrum form a part of the feature of the vegetation of the arid, depressed portions of the North-west Coast,* where several of the more harsh, rigid kinds of plants, of various genera, of the South Coast have been remarked. Those extensive shores (generally speaking) are not wanting in the order, for two species of the tropical genus Santalum, Exocarpus, and a globular-fruited Fusanus, were collected in and about the parallel of 15 degrees South.
(*Footnote. Towards the North-west Cape.)