of Australia.'] INTRODUCTORY ESSAY. CV 



the scarce old forms, and a strong ally of those already common : nor can it he doubted but that 

 many of the small local genera of Australia, New Zealand, and South Africa, will ultimately disappear, 

 owing to the usurping tendencies of the emigrant plants of the northern hemisphere, energetically 

 supported as they are by the artificial aids that the northern races of man afford them. 



On some of the Naturalized Plants of Australia. 



My sources of information upon this subject are unfortunately extremely scanty, and almost con- 

 fined to data procured from the vicinity of Melbourne, where Mr. Adamson has paid especial atten- 

 tion to the introduced species which have run wild, and assumed the positions and importance of 

 native plants. It would be interesting to discover the date and particular circumstances under 

 which these plants were introduced, and so to register their increase and migrations as to afford 

 to succeeding observers the means of comparing their future condition with their present. In the 

 early times of a colony, there is comparatively little difficulty in distinguishing the colonists from 

 the native species ; but as the surface of the land becomes artificially disturbed, the habits of all its 

 plants are influenced, — the endemic species are driven from their native places, and take refuge in 

 hedgerows, ditches, and planted copses, and from there associating with the introduced plants, are 

 apt to be classed in the same category with them ; whilst the introduced wander from the cultivated 

 spots and eject the native, or, taking their places by them, appear, like them, to be truly indigenous. 



There are many interesting subjects of inquiry connected with this replacement of one vegetable by 

 another, such as determining the relations between the facility with which the new plants of certain coun- 

 tries or genera are introduced and establish themselves, and the countries such plants come from, or 

 Floras of which they form a part.* Much of course depends on the new comer finding a suitable 

 climate and soil for its future increase, but there may be more in the physique or constitution of the 

 new comer that enables it to displace other plants which are apparently equally well (if not better) 

 adapted to the circumstances it finds itself environed with. The nature of the past intercourse be- 

 tween Europe and Australia should lead us to anticipate that a far greater number of English plants 

 are naturalized in Australia than of Australian in England ; but the fact of importation does not 

 explain naturalization, nor how it is that no Australian plant has become naturalized in England. 

 This total want of reciprocity in migration is no doubt mainly attributable to climate, but then we 

 have the apparent double anomaly, that Australia is better suited to some English plants than Eng- 

 land is, and that some English plants are better suited to Australia than those Australian plants were 

 which have given way before English intruders. For my own part, I am disposed to consider that 

 the three elements of (1) abundant exportation of seed from Europe into Australia for agricultural 

 and horticultural purposes, and scanty export of Australian seed produce to England ; (2) better 

 adaptation of Australia than England to support numerous forms of vegetable life; and (3) abun- 

 dance of unoccupied ground in Australia as compared with England ; are, combined, all but sufficient 

 to account for the predominance of so many European naturalized plants in Australia, and for the 

 converse state of things in England. But I think it may still remain to be seen whether the altered 



* The reader will find some admirable discussions on this and kindred subjects in the chapters of A. D, a Can- 

 dolie's ' Geographie Botanique Raisormee ' devoted to naturalized and introduced plants. 



