W. Travers. — On the Spread of Cassiiiia leptophylla. 249 



it afFectecl the pastoral occupiers, the results of which I will mention in tho 

 sequel. I have, moi'eover, heard that this plant is already interfering greatly 

 with the use of the natural pastures on the east coast of the North Island, 

 more particularly within the Wellington Province ; and that sheep-farmers 

 there are looking upon its presence as a very serious and not easily preventible 

 evil. But before mentioning the results of my enquiries in regard to it, I 

 propose to notice a few interesting facts, most of which have come under my 

 own observation, in connection with what Dr. Hooker has termed the 

 " replacement of species," a term used by him to designate the permanent 

 changes which take place in the flora of a new country, as the result of the 

 introduction of competing foreign organisms. The facts which I purpose 

 mentioning, however, though properly associated with such permanent effects, 

 relate only to certain temporary changes in the character of the introduced 

 vegetation, not brought aboiit intentionally or by the direct application of labour. 



In former papers, read before this Society, I pointed out that accli- 

 matization (a term, by the way, which I object to as involving a fallacy, and 

 which I think ought to be replaced by ' naturalization'), or the introduction of 

 foreign organisms into a country presenting suitable conditions for their 

 growth and subsistence, is the result of both intentional and unintentional 

 action on the part of man. His intentional action is usually directed to the 

 attainment of beneficial ends, but is constantly accompanied (unavoidably to a 

 certain extent) by mischievous results. Of these latter I may instance the 

 introduction of various forms of Coccus and Aphis; and of the larvae of various 

 species of destructive Coleoptera and Diptera, most of which have been 

 brought in Wardian cases ; and of the seeds of innumerable weeds, such as 

 those of Ruinex, Stellaria, Hypochoeris, Euphorbia, etc. I also pointed out the 

 results which are usually produced upon the indigenous vegetation in countries 

 previously unoccupied by civilized man, by the introduction of animals and of 

 competing foreign organisms. 



It must not, however, be supposed that the struggle thus brought about 

 between the introduced and indigenous forms of life is a mere battle between 

 these two forces, for, in reality, each individual species concerned, whether 

 local or foreign, is fighting " on its own hook," striving against all as against 

 a common enemy, and seeking to secure for itself the greatest share in 

 ultimate occupation. As may be understood, many of the combatants, if not 

 altogether disabled, are seriously enfeebled, whilst the fortunes even of those 

 which are able to show the strongest front are somewhat various. Now, we 

 know that in the hill districts of both islands of New Zealand the chief object 

 of the European settler is to I'eplace the native vegetation by grasses suitable 

 for the maintenance of cattle and sheep, and various processes, more or less 

 direct in their action, are employed in order to attain this end. 



Pi 



