The miscellaneous botanical works of Robert Brown/Volume 1/General view of the botany of Swan River
BOTANY OF SWAN RIVER.
ROBERT BROWN, ESQ., F.R.S.
[Extracted from the 'Journal of the Royal Geographical Society of
London.' Vol. I, pp. 17–21.]
GENERAL VIEW OF THE BOTANY
VICINITY OF SWAN RIVER.
By R. BROWN, Esq., F.R.S.
Read November 22nd, 1830.
The vegetation of the banks of Swan River, and of [17 the adjoining country to the southward, is at present known chiefly from the report of Mr. Charles Fraser, the botanical collector, who accompanied Captain Stirling in his examination of that district in 1827, and from collections of specimens which were then formed.
I have inspected, and in part examined, two of these collections; one of which I received from Mr. Fraser himself, through my friend Alexander Macleay, Esq. the Secretary of the Colony of New South Wales; for the second I am indebted to Captain Mangles.
The number of species in both collections does not exceed one hundred and forty; and some dicotyledonous herbaceous tribes, as well as grasses Cyperaceæ and Orchideæ, are entirely wanting.
From materials so limited in extent, but few general observations can be hazarded on the vegetation of this portion of the south-west coast of New Holland.
The principal families of plants contained in the collections are Proteaceæ; Myrtaceæ; Leguminosæ, such especially as belong to Decandrous Papilionaceæ, and to the Leafless Acaciæ; Epacrideæ; Goodenoviæ; and Compositæ. And the more conspicuous plants, not belonging to any of these families, and which greatly contribute to give a character to the landscape, are, Kingia Australis, a species of Xanthorrhæa; a Zamia, nearly allied to, and perhaps not distinct from, Z. spiralis of the east coast, although it is frequently to attain the height of thirty feet; a species of Callitris; one or two of Casuarina; an Exocarpus, probably not different from E. cupressiformis; and Nuytsia floribunda, a plant hitherto referred to Loranthus, but sufficiently distinct in the texture and form of its fruit, and now named in memory of the discoverer of that part of the coast to which this very singular tree is nearly limited.
If an opinion were to be formed of the nature of the country merely from the inspection of these collections, it certainly would be extremely unfavourable as to the quality of the soil; for not only do the prevailing families already enumerated, but the whole of the genera of those families, and even many of the species, agree with those found on the shores of King George's Sound, which, with the exception of a few patches of very small extent, seem absolutely incapable of cultivation.
The opinion so formed, however, would be necessarily modified in noticing the entire want in the collection of 18] tribes, all of which must be supposed to exist, and some even in considerable proportion, in the tract examined; in allowing for the unfavourable season when the herbarium was collected; in admitting the statements in Mr. Fraser's report, respecting the abundance and luxuriance of Anthistiria australis—the Kangaroo-grass of New South Wales; from the account given in the same report of the extraordinary size of some arborescent species of Banksia, which, in the neighbourhood of King George's Sound, generally form small trees only; and lastly, in adverting to the important fact stated by Captain Stirling in his despatch to Government—namely, that the stock had not only been supported through nearly the whole of the dry season, but that most descriptions of it had even fattened on the natural herbage of the country.
From these more general observations I proceed to make a very few remarks, chiefly relating to the geographical distribution of some of the families or more interesting species, either contained in the herbarium, or distinctly noticed in Mr. Fraser's report.
The striking resemblance in general character, and the identity of many of the species with those of King George's Sound, have been already mentioned. But this portion of the shores of New Holland, extending from Swan River on the west coast to Middle Island, in 123° 10' east long. on the south coast, may be said to contain the greatest proportion of those genera which form the chief peculiarities of New Holland vegetation.
In comparing the Flora of the district of Swan River with more distant regions of the same continent, it may be remarked, that probably not more than four or five species are common to this part of the west coast, and to the same parallel of the east coast of New Holland; and that even the existence of some of these species at Swan River is not altogether certain.
In the collections which I have examined there is no specimen of Anthistiria australis, or Kangaroo-grass of New South Wales; but as this valuable grass must have been well known to the botanical collector, and as it is perhaps the most general plant in New Holland, I have no hesitation in admitting its existence on the authority of Mr. Fraser's report.
Mesembryanthemum æquilaterale is neither contained in the herbarium, nor mentioned by the collector. I find, however, in one of the letters from Swan River, published by Mr. Cross, a plant noticed as a pot-herb, that, from the account of the writer, is probably this plant, which, next to Anthistiria australis, is perhaps the most widely diffused species in the Flora of New Holland.
The third species is Pteris esculenta, the only fern found by Mr. Fraser, and which is both general and abundant beyond the tropic in New Holland and in Van Diemen's Land. 19] The Zamia, already noticed, if not specifically different from spiralis, would furnish another example of a plant peculiar to New Holland, and very generally found in the extra-tropical parts of that continent. I had, however, myself observed on the south coast a Zamia of at least ten feet in height, which I suspected might be distinct from Z. spiralis of the neighbourhood of Port Jackson, and which is probably the same with that of Swan River.
The Exocarpus of the Swan River may possibly differ from cupressiformis, though there is nothing in the specimens to make it probable that it is specifically distinct. But Exocarpus cupressiformis is found very generally, not only in the southern parts of New Holland and Van Diemen's Land, but also within the tropic.
The last plant in the collection whose range is very extensive remaining to be noticed, I have not been able to distinguish from Arenaria marina of the shores of Europe.
Of the families existing in the vicinity of Swan River, the most striking, as well as the most extensive, is Proteaceceæ, a tribe which, from its general dispersion, and the remarkable forms of its numerous genera and species, includes many of the chief peculiarities of the vegetation of New Holland.
In Mr. Fraser's collection, the principal genera of this order are—Petrophila, Isopogon, Hakea, and Banksia; and these are also the most abundant in the districts of King George's Sound and of Lucky Bay. The number of species of the two first-mentioned genera confirms the remark made in the "Botanical Appendix to Captain Flinders's Voyage—namely, that in New Holland, at the western extremity of the parallel of latitude in which the great mass of this order of plants is found, a closer resemblance is observable to the South African portion of the order than on the east coast, where those allied to the American part chiefly occur.
This is not the place to enter into a particular account of the new species of this family existing in the collections from Swan River. I may observe, however, that the number is considerable, and that their specific characters have been recently published.
The Myrtaceæ of Swan River belong chiefly to Melaleuca, Beaufortia, Calothamnus, Calythrix, Billotia, and Eucalyptus.
Of Eucalyptus the only species in the collection had been first found in Captain Flinders's voyage at King George's Sound, on the shores of which it was the only useful [20 timber tree, though there of very moderate size. I have named it Eucalyptus calophylla.
Mr. Fraser describes it as forming, on the banks of the Swan, a large forest tree, and erroneously refers it to Angophora, a genus which is limited to the east coast of New Holland. Other species of Eucalyptus, forming the timber of the country, are mentioned in the report, and considered to be some of the common gum-trees of Port Jackson, from which, however, I have no doubt they will prove to be distinct; for I am acquainted with no species of this genus common even to the east and south coasts of New Holland.
I shall conclude with a remark relating equally to the genus Eucalyptus and to the Leafless Acaciæ, several species of which are found in the collection. This observation I have formerly made in the Appendix to Captain Flinders's Voyage in the following terms:—"These two genera are not only the most widely diffused, but by far the most extensive in Terra Australis, about 100 of each having already been observed; and if taken together, and considered with respect to the mass of vegetable matter they contain, calculated from the size as well as the number of individuals, are perhaps nearly equal to all the other plants of that country. They agree very generally also, though belonging to very different families, in a part of their economy, which contributes somewhat to the peculiar character of the Australian forests, namely, in their leaves, or the parts performing the functions of leaves, being vertical, or presenting their margin, and not either surface, towards the stem: both surfaces having consequently the same relation to light.
"This economy, which uniformly takes place in the Acaciæ, is in them the consequence of the vertical dilatation of the foliaceous footstalk; while in Eucalyptus, where, though very general, it is by no means universal, it proceeds from the twisting of the footstalk of the leaf."
To this quotation it may be added that these two genera still more uniformly agree in the similarity of the opposite surfaces of their leaves. But this similarity is the indication of a more important fact—namely, the existence equally on both surfaces of the leaf, of those organs, for which, as I believe them to be in general imperforated, I have adopted the name of cutaneous glands, but which by most authors are denominated pores, or stomata of the epidermis.
In leaves, especially of trees and shrubs, these glands are generally found on the under surface only; while among arborescent plants in a very few instances, as in several Coniferæ, they are confined to the upper surface.
21] In addition to the two extensive New Holland tribes here mentioned, there are many other cases in which these organs occupy both paginæ; and I am inclined to think such cases more frequently occur on that continent than in any other part of the world. It is at least certain that on this microscopic character, of the equal existence of cutaneous glands on both surfaces of the leaf, depends that want of lustre which is so remarkable in the forests of New Holland.