OCR Text |
Show 462 ISLAND LIFE. (PART H. . · d f 1 · th Indian or Malayan Nearly500of its speCies are I eniCa Wl h'l th lants or are very close representatives of them; w I e ere p ' 200 I d' O'enera confined for the most part to are more than n Ian o ' . . 1 t' f Australia. The remamder of the tro-the tropica por IOn ° . f · fl · t of certain speCies and genera o temperate pical ora conSIS S . t b t h l Austra 1. a wh I'C h ranO'e over the whole contmen , . u t ese o . 11 Portion of the peculiarly Australian genera. form a very sma . . These remarkable facts clearly pomt to one. conclusiOn-that the flora of tropical Australia is, comparatively, recent a~d d en·v at 1' ve. If w e I·maOo 'I·ne the oO 'reater part of North Austra.h a to h ave b ecn SubmeroO 'ed beneath the ocean, f.r om wh.i Ch it rose in the middle or latter part of the Tcrtrary p~nod, ff o er·m g an ex tensive area ready to be cov. ered by su. ch s. mtablc ~ f eO'etation as could first reach It, somethmg hke the 1orms o v o . . · F h t clition of thinO'S would Inevitably anse. ~rom t c presen con o ld · k - north widespread Indian and Malay pl~nts wou qmc ly t h.l from the south the most dommant forms of tern-en er, w 1 e h · 1 t A t pera e us rar I a , and such as .w ere b.e st ada.p ted to t c trop1ea. . climate and arid soil, ~ould 1ntermmgle with them. Even .1f numerous islands had occupied the area of Northern Australia for long periods anterior to the final elevation, very much the same state of things would result. . The existence in North and North-east Austraha of enormous areas covered with Cretaceous and other Seconda,ry <leposit~, as well as extensive Tertiary formations, lends support to the v1ew, that during very long epochs temperate Australia was cut off from all close connection with the tropical and northern lands by a wide extent of sea; and this isolation is exactly what was required, in order to bring about the _wonderf~l amount of specialisation and the high development mamfested by the species than the former." This, ho":e':er, appc~rs to mo to ~e hardly a case in point, because Europe is a d1stmct continent from Afnca and has had a very different past history. A closer parallel ~ay perhaps b? found iu equal areas of Brazil and south temperate Amenca, or of MeXIco and the Southern United States, in both of which cases I suppose there can be little doubt that the tropical areas are far the richest. Temperate So~Ith Africa is, 110 doubt, always quoted as richer than an equal area of trop.lC~l Africa or perhaps than any part of the world of equal extent, but this 18 arlmitted to be an exceptional case. CllAP. XXII.] '!'liE FLOllA OF NEvV ZEALAND. 463 typical Australian flora. Before proceeding further, however let us examine this flora itself, so far as regards its component parts and probable past history. The Floras of South-eastern and South-western Australia.Thc peculiarities presented by the south-eastern and southwestern subdivisions of the flora of temperate Australia are ~ost' interesting and suggestive, and are, perhaps, unparalleled m any other part of the world. South-west Australia is far less extensive than the south-eastern division-less varied in soil and climate, wjth no lofty mountains: and much sandy desert; yet, strange to say, it contains an equally rich flora and a far ?Teater proportion of peculiar species and genera of plants. As S1r Joseph Hooker remarks :-"What differences there arc in conditions would, judging from analogy with other countries, favour the idea that South-eastern Australia, from its far greater area, many large rivers, extensive tracts of mountainous country and humid forests, would present much the most extensive flora, of which only the drier types could extend into Southwestern Australia. But such is not the case; for though the far greater area is much the best explored, presents more varied conditions, and is tenanted by a larger number of Natural Orders and genera, these contain fewer species by several hundreds.'' 1 The fewer genera of South-western Australia are due almost wholly to the absence of the numerous European, Antarctic, and South-American ,types foundj in the south-eastern region, while in purely Australian types it is far the richer, for while it contains most of those found in the east it has a larO'e 0 number altogether peculiar to it; and Sir Joseph Hooker states · that "there ar<; about 180 genera, out of 600 in South-western Australia, that are either not found at all in South-eastern or ' 1 Sir Joseph Hooker thinks that later discoveries in the Australian Alps and other parts of East and South Australia may have greatly modified or perhaps reversed the above estimate. But even if this should be the case t?e small area of South-wE'st Australia will still be, proportionally, far the ncher of the two . . It is much to be desired that the enormous mass of facts contained in Mr. Bentham's Flom Australiensis should be tabulated and compared by some competent botanist, so as to exhibit the various r~lations of its wonderful vegetation in the same manner as was done by S1r Joseph Hooker with the materials availtJ.ble twenty-one years ago. |