INTRODUCTORY ESSAY. 39 



portance attached to locality, we believe that botanists have 

 no conception. Witness the fact, that several common Euro- 

 pean garden-plants introduced into the grounds of the British 

 Resident at Katmandu (Nipal), and thence re-imported to 

 England, have been at once put forth in this country as new 

 Himalayan discoveries, and specific characters invented for 

 them. But instances of this multiplication of names are 

 almost incredibly numerous : the common English Yew has 

 two Himalayan names; the Pteris aquilina (English Bracken), 

 seven ; the eighteen known Indian species of Clematis are in 

 Steudel's ' Nomenclator' ranked under forty names; and we 

 may conclude by announcing our conviction, that more than 

 one-half of the recorded species of Indian plants are spuri- 

 ous, and that in many natural orders the undescribed species 

 hardly equal in number those which require to be cancelled. 



The fact that almost every Himalayan plant has a vertical 

 range of nearly 4000 feet, and many of 8000, is in itself a 

 suggestive one. Several hundred species are dispersed from 

 the Levant to the Indus, and many more from the Ganges 

 to the Chinese Sea. Such instances of distribution in tropical 

 plants are called strange and exceptional by unreflecting bo- 

 tanists, who forget how many species are common to aU longi- 

 tudes between England and Kamtchatka, or to all the moun- 

 tains of Europe ; or to the Eocky Mountains of America, and 

 those of Scotland and Norway; or to all latitudes between 

 England and North Africa. 



The subject of geographical distribution leads to questions 

 of practical importance, upon which we have a few remarks 

 to offer, as eminently bearing upon aU questions relating to 

 the treatment of a systematic flora : these are, — 1. Its depend- 

 ence on the doctrine of specific centres. 3. The power of 

 migration as capable of effecting the present distribution. 3. 

 The general effects of migration in producing a much wider 

 dispersion and ubiquitous diffusion of species than is generally 

 admitted by botanists who have not investigated tropical 

 floras, and especially continental ones. 



