418 MUTABILITY IN THE VEGETABLE KINGDOM. CHAP. xxi. 



of perpetual snow in the Himalaya, and having specially 

 devoted his attention to ( geographical varieties,' or those 

 changes of character which plants exhibit, when traced over 

 wide areas and seen under new conditions ; being also prac 

 tically versed in the description arid classification of new 

 plants, from various parts of the world, and having been 

 called upon carefully to consider the claims of thousands of 

 varieties to rank as species, no one was better qualified by 

 observation and reflection to give an authoritative opinion on 

 the question, whether the present vegetation of the globe is 

 or is not in accordance with the theory which Mr. Darwin 

 has proposed. We cannot but feel, therefore, deeply inte 

 rested when we find him making tbe following declaration : 

 ( The mutual relations of the plants of each great botanical 

 province, and, in fact, of the world generally, is just such as 

 would have resulted if variation had gone on operating 

 throughout indefinite periods, in the same manner as we see 

 it act in a limited number of centuries, so as gradually to give 

 rise in the course of time, to the most widely divergent forms.' 

 In the same Essay, this author remarks, ' The element of 

 mutability pervades the whole Vegetable Kingdom ; no class, 

 nor order, nor genus of more than a few species claims abso 

 lute exemption from it, whilst the grand total of unstable 

 forms, generally assumed to be species, probably exceeds 

 that of the stable.' Yet he contends that species are neither 

 visionary, nor even arbitrary creations of the naturalist, but 

 realities, though they may not remain true for ever (p. 11). 

 The majority of them, he remarks, are so far constant, 

 4 within the range of our experience,' and their forms and 

 characters so faithfully handed down, through thousands of 

 generations, that they admit of being treated as if they were 

 permanent and immutable. But the range of ' our experi 

 ence ' is so limited, that it will not account for a single fact 

 in the present geographical distribution, or origin of any one 



