they are not entirely neglected, but receive some consideration 

 when certain cases of distribution are discussed. 



Generally in researches dealing with phytogeographical dis- 

 tribution, the vegetation receives no consideration, the 

 distribution of the species being alone the theme. Such treat- 

 ment of the subject is not on natural lines. The species are 

 the ultimate units of the vegetation, and its distribution includes 

 that of the species. Once a species has become a member of one 

 or more plant-associations, its movements are apparently 

 governed by those of the associations to which it belongs. The 

 dynamics of plant-distribution, except before an association is 

 stabilized, is not a moving of individual species, but of plant- 

 associations. Once an association has become stable, it can 

 receive only with the most extreme difficulty additional species 

 from elsewhere. The gradual evolution of the association has 

 led to rigorous selection and the final product is perhaps the 

 most epharmonic that the species available would permit. For 

 one hundred years, or thereabouts, a gradually increasing band 

 of plant-immigrants has attempted to gain a footing in the 

 virgin associations of New Zealand, and yet, despite the many 

 millions of seeds cast forth yearly, not one introduced plant has 

 been able to gain a place in any purely virgin plant-association, 

 if certain water and rock associations be excepted. Foreign 

 plants there are in profusion growing wild throughout the 

 length and breadth of the islands along with the indigenous 

 species, but this is only in those plant-associations which have 

 been directly or indirectly modified or brought into existence by 

 the action of man himself, his grazing animals, or his fires 3 . 



As this lecture treats of plant-distribution in New Zealand 

 it might well be expected that I should say something regarding 

 Willis's "Age and Area Theory," since that distinguished author 

 bases it to no small extent on the distribution of the vascular 

 plants of New Zealand*. However, at the present time, I have 

 not the leisure to deal with that important generalization, since, 

 apart from special crticisms, I should like to examine it by 

 means of a quite different set of figures from those used by 

 Willis which would take into consideration not merely latitudinal 

 distribution in one plane, but would deal also with vertical dis- 

 tribution and distribution according to the plant-formations, or 

 even the clearly marked plant-associations. Nor do I think that 

 the distribution of the high-mountain plants a flora, as may 

 be seen further on, amply distinct from those of the lowlands 

 and sea-coast can be treated along with the two last-mentioned 

 floras. The flora of the high-mountains is essentially a South 

 Island and Stewart Island matter, for the paucity of the North 



3 - For a detailed account of the behaviour of the introduced plants in New 

 Zealand see Cockayne, L., "New Zealand Plants and their Story," Ed. 2, 1919, 

 pp. 144-158. 



4. Willis, J. C., "The Distribution of Species in New Zealand," Ann. Bot., 

 vol. xxx, 1916, pp. 437-57, together with other papers on New Zealand distribution 

 which have appeared in the same journal at later dates. 



