AUSTEALIJLN FEKNS. 41 



well as in Europe ; whilst Sir W. Hooker has recently demon- 

 strated the identity of our Pteris esculenta, and Aspidium proli- 

 ferum, with Pteris aquilina, and Aspidium aculeatum. It seems 

 probable that as our knowledge progresses, and opportunities 

 present themselves for comparing cultivated ferns from different 

 parts of the world, we shall arrive a-t the conclusion that other 

 species are identical, although in their wild state, owing to the in- 

 fluence of soil and climate, they assume forms so different that, in 

 the present state of science, they must necessarily be ranged as 

 distinct species. And this, no doubt, has been the case in the 

 vegetable kingdom generally, and seems in a great degree to have 

 contributed to the loose and inaccurate manner in which s^me 

 persons speak of species, just as if, in a long course of time, 

 species and even genera have become mingled together, and that 

 the fruit tree, which was created only " to yield fruit after his 

 kind," may so deviate from the original type as to be no longer 

 referable to the same place in the vegetable kingdom to which it 

 was destined by the Creator. It would certainly remove many 

 difficulties from the philosophic mind if we could believe that the 

 true theory had been discovered, where 1 >y " a multitude of geo- 

 logical facts otherwise unaccounted for" might be satisfactorily 

 explained ; and whereby it could be demonstrated that the 

 varieties of the human family not merely sprang from one single 

 pair, as Revelation assures us, but that " the long-continued in- 

 fluence of external circumstances gave rise to peculiarities in- 

 creased in many successive generations, and at length fixed them 

 by hereditary transmission." But alas ! so far as the vegetable 

 kingdom is concerned, the hypothesis that " any species is ca- 

 pable of varying indefinitely from its original type," is flatly 

 contradicted by the experience of many generations, during which 

 no material change has been made in the characters and forms 

 of species. Dr. Hooker, in his Introductory Essay to the Flora 

 of Australia, " contends that species are neither visionary, nor 

 even arbitrary creations of the naturalist, but realities, though 

 they may not remain true for ever." He then candidly adds 

 that " the majority of them are so far constant 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," 

 p 



