1843— 1882] N. AMERICAN FLORA 429 



But there is another question in your last letter — one Letter 328 

 about which a person can only give an impression — and 

 my impression is that, speaking of plants of a well-known 

 flora, what we call intermediate varieties are generally less 

 numerous in individuals than the two states which they 

 connect. That this would be the case in a flora where things 

 are put as they naturally should be, I do not much doubt ; and 

 the wider are your views about species (say, for instance, with 

 Dr Hooker's very latitudinarian notions) the more plainly 

 would this appear. But practically two things stand hugely 

 in the way of any application of the fact or principle, if such 

 it be. I. Our choice of what to take as the typical forms 

 very often is not free. We take, e.g., for one of them the 

 particular form of which Linnaeus, say, happened to have a 

 specimen sent him, and on which [he] established the species ; 

 and I know more than one case in which that is a rare form 

 of a common species ; the other variety will perhaps be the 

 opposite extreme — whether the most common or not, or will 

 be what L. or [illegible] described as a 2nd species. Here 

 various intermediate forms may be the most abundant. 

 2. It is just the same thing now, in respect to specimens 

 coming in from our new western country. The form which 

 first comes, and is described and named, determines the 

 specific character, and this long sticks as the type, though 

 in fact it may be far from the most common form. Yet of 

 plants very well known in all their aspects, I can think of 

 several of which we recognise two leading forms, and rarely 

 see anything really intermediate, such as our Mentha borealis, 

 its hairy and its smooth varieties. 



Your former query about the variability of naturalised 

 plants as compared with others of same genera, I had not 

 forgotten, but have taken no steps to answer. I was going 

 hereafter to take up our list of naturalised plants and consider 

 them — it did not fall into my plan to do it yet. Off-hand I 

 can only say that it does not strike me that our introduced 

 plants generally are more variable, nor as variable, perhaps, 

 as the indigenous. But this is a mere guess. When you 

 get my sheets of first part of article in Sillitnan's Journal, 

 remember that I shall be most glad of free critical comments ; 

 and the earlier I get them the greater use they will be to 

 me. . . . 



