FLORA OF TASMANIA. [Fossil Plants, Geology, etc., 



peninsula, except the western coast and mountains, the valley of the Irrawaddi, and the lower 

 flat districts of the Malay Islands, whence it is continued in great force over the whole of tropical 

 Australia. 



Reversing the position, and beginning at the southern extreme of this arc of vegetation, there is 

 first the Antarctic Flora (the complement of the Scandinavian), with its decided Australian represen- 

 tatives in Centrolepidece and Stylidiem, commencing in Fuegia, the Falklands, and Lord Auckland's and 

 Campbell's group, reappearing in the alps of New Zealand, Tasmania, and Australia, and disappearing 

 under the equator, on the alps of Borneo, being thus strictly confined to the southern hemisphere. 

 Next there is the Australian Flora proper, a large and highly developed one, diminishing rapidly after 

 crossing the southern tropic, and as it advances towards the north-western shore of the continent, 

 reappearing in very small numbers in the Malay Islands, and terminated by a Casuarina on the east 

 coast of the Bay of Bengal, and a Stylidium on the west. Not one representative of this vegetation 

 advances further north-west. 



Analogous appearances are presented by Africa and America. In Africa Indian forms prevail 

 throughout the tropics, and, passing southwards, occupy the northern boundary of the south tempe- 

 rate zone ; but there a very copious and widely different vegetation succeeds, of which but few repre- 

 sentatives advance north to the tropic, and none to India, but with which are mingled Scandinavian 

 genera and even species. In the New World, Arctic, Scandinavian, and North American genera and 

 species are continuously extended from the north to the south temperate and even Antarctic zones ; 

 but scarcely one Antarctic species, or even* genus (Forstera, Calceolaria, Colobatithus, Gunnera, etc. 

 etc.) advances north beyond the Gulf of Mexico. 



These considerations quite preclude my entertaining the idea that the Southern and Northern 

 Floras have had common origin within comparatively modern geological epochs ; ' on the contrary, 

 the European and Australian Floras seem to me to be essentially distinct, and not united by those 

 of intervening countries, thougli fragments of the former are associated with the latter in the southern 

 hemisphere. For instance, I regard the Indian plants in Australia to be as foreign to it, botanically, 

 as the Scandinavian, and more so than the Antarctic ; and that to whatever lengths the theory of varia- 

 tion may be carried, we cannot by it speculate on the Southern Flora being directly a derivative one 

 from the existing Northern. On the contrary, the many bonds of affinity between the three southern 

 Floras, the Antarctic, Australian, and South African, indicate that these may all have been members 

 of one great vegetation, which may once have covered as large a southern area as the European now 

 does a Northern. It is true that at some anterior time these two Floras may have had a common 

 origin, hut the period of their divergence autedates the creation of the principal existing generic 

 forms of each. To what portion of the globe the maximum development of this Southern Flora 

 is to be assigned, it is vain at present to speculate; but the geographical changes that have re- 

 sulted in its dismemberment into isolated groups scattered over the Southern Ocean, must have 

 been great indeed. Circumscribed as these Floras are, and encroached upon everywhere by northern 

 forms, their ultimate destiny must depend on that power of appropriation in the strife for place which 

 we see in the force with which an intrusive foreign weed establishes itself in our already fully peopled 

 fields and meadows, aud of the real nature of which power no conception has been formed by natu- 

 ralists, and which has not even a name in the language of biology. Everywhere, however, we see the 

 more widely distributed, and therefore least peculiar forms of plants, spreading, and the most pecu- 

 liar dying out in small areas, and the progress of civilization has introduced in man a new enemy to 

 * Aetna is a remarkable exception. See p. xc. in note. 



