A COMMENTARY 
ON 
Mr. HEMSLEY’S INTRODUCTION AND APPENDIX 
TO THE 
BOTANICAL PART OF THE ‘BIOLOGIA CENTRALI-AMERICANA.’ | 
By Sir J. D. HOOKER, Late Director oF THE RoyaL GARDENS, Kew. 
Havine been deeply interested in the progress of Mr. Hemsley’s work on the Botanical 
portion of the ‘ Biologia Centrali-Americana,’ and especially in that author’s elaboration 
of the important Appendix relating to Botanical Geography, which is contained in the 
fourth volume, I have been requested by Messrs. Salvin and Godman to contribute to 
the pages of their ‘ Biologia’ some observations of my own relating to the scope and 
character of the work accomplished by Mr. Hemsley, especially as regards its value 
as advancing knowledge of the geographical distribution of plants. 
At the same time, I have been asked to add, to any comments of my own upon the 
contents of the Appendix, my conceptions of the principles which should guide the 
_ botanical geographer in the limitation of the primary botanical regions of the globe— 
conceptions which have been tardily matured, during botanical visits to many countries 
and a long familiarity with the dominant features of their Floras, obtained both on 
the spot and from a study of large herbaria. 
No country of equal area presents a richer or more varied vegetation than Mexico. 
Except perhaps the Javan and Indian, no tropical Flora of great extent is so well 
explored and so fully represented by collections; and none has been subjected to so 
searching an analysis, in respect of the correlation of its botanical features and the defi- 
nition of its botanical regions, as has this Flora under Mr. Hemsley’s judicious, pains- 
taking, and accurate methods of study. My view of the merit and completeness of 
this part of the work urged me to suggest to the authors of the ‘ Biologia’ the desira- 
