INTRODUCTORY ESSAY. 57 



respectively of the Caspian steppes and North Persia on the 

 one hand, and of Siberia on the other, have been described by 

 Rnssian botanists, and especially by Ledebonr, Bunge, Tur- 

 czaninow, C. A. Meyer, and Fischer, besides being rendered 

 classical by the labours of Gmelin and Pallas, 



Boissier's * Diagnoses Plantarum Orientalium/ published in 

 the € Annales des Sciences Naturelles/ contain descriptions of 

 many new Persian and Levantine plants, mainly from the 

 collections of Kotschy and Auchcr-Eloy, which are also com- 

 mon to Western Tibet, Afghanistan, Sind, and Beluchistan. 

 We have largely availed ourselves of the excellent descriptions 

 in these diagnoses, though differing from their truly learned 

 author in his estimate of the influence of climate and the 

 effects of variation. M. Boissier's knowledge of the South 

 European and Mediterranean flora is, we believe, unrivalled, 

 and derived from personal experience acquired during several 

 years spent in exploring indefatigably the Spanish, Grecian, 

 and Oriental floras, of which we have numerous representa- 

 tives in India, and we therefore record our dissent from the 

 views of so great a botanist, on the limits of species especially, 

 with the most sincere respect, and with considerable diffidence. 

 It would be out of place here to enumerate the European 

 and Mediterranean Floras of which we have made daily use ; 

 there are few of them that we have not been obliged to con- 

 suit, especially with reference to the critical discrimination of 

 plants belonging to such genera as Ranunculus, Delphinium, 

 Aconitum, etc., etc. So many of these floras are mere com- 

 pilations, or made up of local varieties ranked as species, or 

 studies of the plants of particular areas, treated of without 

 reference to their value as members of the vegetable kingdom, 

 that we find ourselves, when studying any of the large Euro- 

 pean genera, plunged into a maze of difficulties, to extricate 

 ourselves from which it has been necessary to work out each 

 species ab initio , and from a study of all its forms. Koch's 

 1 Flora Germanica' for descriptions, and Reichenbach's ' Ieoncs' 

 for illustrations, are both accurate and useful; and in Vivi- 



i 



