360 THE CANADIAN NATURALIST. [June 



mediate localities. An empirical grouping of allied plants for the 

 purpose of distribution may thus lead to a practical solution of 

 difficulties in the classification and synonymy of species. 



My thus grouping names must not therefore be regarded as a 

 committal of myself to the opinion that the plants thus grouped 

 are not to be held as distinct species ; I simply treat of them 

 under one name, because for the purposes of this essay it appears 

 to me advisable to do so. Every reflecting botanist must acknow- 

 ledge that there is no more equivalence amongst species than there 

 is amongst genera ; and I have elsewhere* endeavoured to show 

 that, for all purposes of classification, species must be treated as 

 groups analogous to genera, differing in the number of distinguish- 

 able forms they include, and of individuals to which these forms 

 have given origin, and in the amount of affinity both between 

 forms and individuals. My main object is to show the affinities 

 of the polar plants, and I can best do this by keeping the specific 

 idea comprehensive. It is always easier to indicate differences 

 than to detect resemblances, and if I were to adopt extreme views 

 of specific difference, I should make some of the polar areas appear 

 to be botanically very dissimilar from others with which they are 

 really most intimately allied, and from which I believe them to have 

 derived almost all their species. A glance at my catalogue will 

 show that, had I ranked as different species the few Greenland 

 forms of European plants (called generally by the trivial name 

 Groenlandica) , I should have made that flora appear not only 

 more different from the European than it really is, but from the 

 American also ; and that the differences thus introduced would be 

 of opposite values, and hence deceptive, in every case when the 

 European species (of which the Groenlandica is often not even a 

 variety or distinct form) was not also common to America. 



I wish it then to be clearly understood that the catalogue here 

 appended is intended to include every species hitherto found 

 within the arctic circle, together with those most closely allied 

 forms which I believe to have branched off from one common 

 parent within a comparatively recent geological epoch, and that 

 immediately previous to the glacial period or since then. Further, 

 I desire it to be understood that I claim no originality in bringing 

 these closely allied forms together ; from the appended notes it will 



* Essay on the Australian Flora ; introductory to the Flora 

 Tasmanica,, etc. 



