134 ORIGINAL ARTICLES. 



know or believe to have had such a common descent. The specific iden- 

 tity of two or more individuals admits, therefore, but very rarely of po- 

 sitive proof ; we must judge of it by inductive evidence, selecting by the 

 careful consideration of what characters are known, especially in allied 

 species, to remain permanent generation after generation, unaltered by 

 change of soil, climate, or other circumstances, and what are the varia- 

 tions occasioned by causes which we can appreciate, or which are known 

 to occur without assignable cause. The conclusions to be derived from 

 such evidence will not, indeed, always be decisive, and different persons 

 will often form different judgments ; but that is an unavoidable conse- 

 quence of the imperfection of the human mind. 



My own attention was first directed to the variations to which plants 

 of the same species are liable, under different circumstances, in the year 

 1820. I had then become tolerably familiar with the common plants 

 of France, in the West, in Upper Languedoc, and in the central Pyre- 

 nees ; and, settling for some years in the neighbourhood of Montpelier, 

 I was struck with the different aspect assumed by several of the same 

 species in this very different soil and climate. In the first instance, I 

 did indeed believe that many of these were representative, not identical 

 species ; but I could not but observe even then that, in many cases, spe- 

 cies really the same underwent considerable modifications, through the 

 influence of soil and climate. In 1823 I collected, with my friend, Dr. 

 Arnott, a considerable number of Scotch specimens, which, two years 

 later, after our Pyrenean tour, we had the opportunity of comparing 

 with a similar vegetation grown in mountains of twice or thrice the ele- 

 vation of the Scotch ones, but under a difference of latitude of 12 to 13 

 degrees ; whilst, on the same Pyrenean chain, we were several times 

 struck with the differences exhibited by plants of the same species grow- 

 ing in the cool northern, or the hot southern valleys. In 1821, on my 

 father's estate near Montpelier, a considerable extent of the botanically 

 rich waste lands, called garrigues, was walled in, to allow the natural 

 wood to grow up ; and, during the few succeeding years, I could observe 

 a gradual, but in many instances very striking, change take place in 

 the character and aspect of the wild plants protected by the enclosure. 

 In 1837, when at Trieste, I visited a similar enclosure, on a larger 

 scale, and of many years' standing, at Lippiza, near that town, and ob- 

 served very marked differences in the individuals of some species, when 

 growing within or without these walls. From the time, indeed, when 

 I first began to collect notes on the vegetation of Southern Europe, some 

 of which I embodied in my " Catalogue des Plantes des Pyrenees et du 

 Bas-Languedoc," published in 1826, my attention has been much di- 

 rected to the modifications of specific types, in all my herborisations in 

 various parts of Europe, and, more especially, in the mountains of Scot- 

 land, the Pyrenees, Central France, and Tyrol ; in the lower hills and 

 plains of France, Britain, Sweden, Germany, Italy, and Sicily ; and on 

 the coasts of Britain, Western and Southern France, and various parts 

 of the Mediterranean, Adriatic, and Black Seas. The preparation of 

 large collections for distribution has given me opportunities of studying 



