no ROBERT SMITH [February 



respectively, yet their floral characters indicate widely separate genetic 

 affinities. 



Warming (1896) has recently subdivided the study of Plant Geo- 

 graphy into two main branches based upon these two different points 

 of view, flora and vegetation : — 



(1) Floristic Plant Geography, which considers questions relating to 



origin, to past and present lines of migration — in short, to 

 the distribution, past and present, of the species ; 



(2) Oecological Plant Geography, which considers the life-forms of 



species, their association, and their relations to the life-con- 

 ditions (heat, light, moisture, food, etc.). 



The vegetation of any region is to be considered then as an associa- 

 tion of plants bound together by the fact that they are all adapted to 

 life in this region. The region may not be uniform throughout its 

 whole area, but may include a great number of sub-associations, each 

 characterised by certain forms of vegetation and determined by par- 

 ticular conditions of life. 



Within each association there are various grades of successful 

 adaptation, and accordingly we find that the plants group themselves 

 as dominant, secondary, and isolated species. 



The study of the vegetation has thus become a study of plant 

 associations — the life-forms which constitute them, the conditions 

 which determine them, and the relations between them. 



The methods for this study are at present by no means well- 

 defined, and probably from the nature of the subject will always remain 

 more or less arbitrary. The differences in the methods employed by 

 the various workers are largely due to the different standpoints from 

 which they view the subject ; whether they regard the vegetation as 

 a term in the description of the scenery, as an index to the meteoro- 

 logical and soil conditions of the country, or as an association of living- 

 organisms. This last aspect is the true biological one, and has steadily 

 gained ground within recent years. 



The first attempt to organise the study of " vegetation " was made 

 by Humboldt in 1806. Before his time travellers had employed 

 the dominant features of vegetation in describing the landscapes they 

 had viewed. Humboldt tried to make these descriptions systematic. 

 From the experience he gained in his wide travels he enumerated the 

 following plant-forms as dominant in different landscapes: — palm, 

 banana, cactus, orchid, mallow, bamboo, mimosa, aloe, grass, fern, lily, 

 willow, myrtle, melastoma, and laurel. He further noted the variations 

 in the proportions of the individuals of different species, how some 

 were social and some isolated (1807, p. 15); and in his definition of 

 the scope of plant geography he says, " C'est cette science qui considere 

 les vdgetaux sous les rapports de leur association locale dans les differens 



