LINNEAN SOCIETY OF LONDON. XXUl 



municate to us some of the numerous observations he has made in 

 geographical entomolog)^ 



Geographical botany has of late years been much attended to, and 

 generally pursued in a right direction. M. A. DeCandoUe, whose 

 great general work on the subject, published in 1855, I have had 

 other opportunities of reporting upon, has resumed some questions 

 concerning it in his paper above quoted, ' Etude sur I'Espece,' in 

 the Bibliotheque Universelle. Dr. Hooker's Essay on the Flora 

 of Australia, already quoted, is the best exposition I am acquainted 

 with of the geographical relations of the flora of any coimtry, and 

 acqxiires a double importance from the peculiarities of that flora. 

 His paper on the Distribution of Arctic Plants, in the 23rd volume of 

 our Transactions, gives us his views of the efiects of climatic changes 

 during the Glacial period on the contraction, extension, or other 

 changes in the area of plants ; and that on the Cedars of Lebanon 

 in the 2nd volume of the Natural History Review is an excellent 

 illustration of representative or geographical species or races. Dr. 

 A, Gray, in his papers illustrative of the Flora of Japan, has worked 

 out the h^-pothesis of an ancient connexion between "Western North 

 America and Eastern Asia at a latitude or with a cHmate admitting 

 of the passage of those North American forms which appear to have 

 travelled across Asia to Western Europe — an idea which I also had 

 taken up in a paper on the Geographical Distribution of British 

 Plants, read at one of your meetings in the close of the year 1858, 

 but vrithdrawn from publication on the appearance of Mr. Darwin's 

 work, which obliged me to reconsider several opinions I had given. 

 Prof. 0. Heer and Count G. de Saporta have, on the contrary, in 

 their above-mentioned investigations of the Flora of the Tertiary 

 period, considered that there is strong evidence of a direct and pro- 

 longed communication across the Atlantic between Europe and 

 North America. Prof. Oliver, however, in the 2nd volume of the 

 Natural History Review, has shown that the facts observed tend 

 rather to confirm Asa Gray's hypothesis of the migration having 

 taken place through Japan. And, generally speaking, botanists seem 

 now to be aware that, although accuracy of detail is, in this, as in 

 every other branch of science the indispensable foundation on which 

 theories must be built, yet, that, as a science, geographical botany 

 does not consist merely in the precise demonstration of the bound- 

 aries of a species fixed, by accidents of soil, cKmate, exposure, or 

 treatment, in one minute portion of the area it occupies, but that, 

 in order to arrive at general results of any value, the whole area 

 must be taken into consideration, and viewed with regard to the 



