LIXXEAX SOCIETY OF LOXDOX. XXXV 



and plan of the work has been recently noticed in an article in 

 ' Nature ' (no. 128, April 11) ; it will therefore be sufficient for me 

 now generally to state that it is in a great measure a development 

 of the paper in Petermann's ' Mittheilungen/ mentioned in mj'^ 

 Address of 1869, mapping out the globe into twenty-four regions of 

 vegetation depending on physical and cKmatological considerations — 

 that it does not touch upon botanical regions depending on com- 

 munity of origin, which the author appears disposed wholly to 

 ignore, or at any rate to relegate to the class of mere hypothesis as 

 yet far too vague to serve as a foundation for any scientific conclu- 

 sions — but that the undoubted influence of climatological and other 

 physical conditions on the progress, dispersion, and life-history of 

 species is here worked out with a care and detail deserving the 

 attention of all physiologists, as well as of all cultivators of exotic 

 plants. I shall on the present occasion confine myself to a few ob- 

 servations on his views with reference to some of those regions or 

 districts to which I had intended to call your attention in my last 

 year's Address. 



One of the most interesting of these regions is the Japanese, or 

 the greater part of Grisebach's Chino-Japanese region — that is, the 

 Japanese islands and opposite coasts of the Asiatic continent. The 

 peculiarities of its flora have been accounted for, upon considerations 

 depending chiefly on origin, in a well-known paper by Asa Gray 

 (Mem. Amer. Acad, new ser. vol. vi. p. 424), whose views are fully 

 coincided in by Maximo wicz and others, but strongly objected to 

 formerly by Miquel and now by Grisebach, who relies upon clima- 

 tological and other physical considerations. It appears to me that 

 this is a strong instance of the combined effects of the two agents, 

 as explained in my above-mentioned Address of 1869 (p. 15 ; Proc. 

 Linn. Soc. 1868-69, p. Ixxvii). The main features of this flora 

 are the mutual intergrafting of northern and tropical types, and the 

 number of highly differentiated endemic or widely dissevered mono- 

 typic or almost monotypic races — the former due to physical, the 

 latter to derivative causes. In the western moiety of the great 

 Old- World continent the northern and tropical floras are widely 

 separated by a double barrier — the great mountain- chain which runs 

 with little interruption from the Atlantic to the Caspian bounding the 

 Mediterranean region to the north, and the great .Ifrican and Arabian 

 deserts which form its southern boundary. Here the only connexion 

 observed from north to south consists in a few European types in- 

 habiting the higher tropical African mountains. Xo tropical forms 

 have been able to cross their northern barriers. In Central Asia 



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