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introductory means of acquiring knowledge. The controversy has 

 latterly got narrowed down into a discussion on the existence or non- 

 existence, in nature, of species : and in his last letter Dr. Ayres 

 brings forward a most extraordinary argument — one, in fact, in which 

 I can scarcely conceive him serious — in support of his views. This 

 argument, which he so triumphantly appeals to, is derived from the 

 inorganic kingdom. Now, Linnaeus and other naturalists do use the 

 term species as applied to certain forms or aggregations of inor- 

 ganized matter, but just in the same way as we should apply the 

 term " species " to a particular kind of chair or table ; while in or- 

 ganic nature it implies a distinct idea connected with the repro- 

 duction of the individuals. I think Dr. A. will require a very little 

 reflection to convince him (I hope he will not be offended at the 

 strength of the term) of the absurdity of such a line of argument. 

 If any naturalist ever used the term species, genus, class, or order in 

 the same sense in the inorganic as in the organic kingdom, I never 

 heard of him. 



The only other point in Dr. Ayres' letter 1 shall notice, is where he 

 wishes to entangle me in a contradiction. I do not happen to have 

 the numbers of 'The Phytologist' in which Dr. Ayres or my own 

 papers are, and therefore cannot quote the exact words ; but if he 

 refers to my letter again, he will see that I do not talk of the " natu- 

 ral " system properly so called, or the systems of Jussieu, Decandolle, 

 or Lindley, as " debris," or unconnected fragments : I only say that 

 if, as Dr. Ayres asserts, every plant and animal has its own peculiar 

 niche in a grand system of nature, considering the paucity of species 

 we are perfectly acquainted with, it must be an unconnected and 

 fragmentary scheme ; so that he will see that my condemnation oi his 

 ideas, and my praise of the " natural " system (whose authors dis- 

 claim his theory,) are perfectly compatible. Enough of this : my 

 best thanks are due to Dr. Ayres for his courtesy throughout 

 our little passage of arms ; and now, save some other champion, 

 not willing to see the immortal Swede, (well and truly called the 

 father of natural science), thrown like useless lumber on the shelf, 

 take up my relinquished lance, this discussion must perforce drop. 



I want to say a word or two on Lastraea recurva of Bree and New- 

 man. This said fern must be very scarce in Scotland ; for anxiously 

 as I have searched for it, I have never yet seen a frond of it grow- 

 ing. As a species, it is one of the most distinct we have ; how it 

 has been so much overlooked and confounded is the only wonder. 

 I think great credit is due to Mr. Bree and Mr. Newman for their 



