XII. TYPES OF DISTRIBUTION. 507 



sentation. But it seems an unwarrantable pre-clecision 

 to assert, that in arranging plants into groups accordant 

 with present peculiarities of distribution, we are in this 

 manner forming them into groups which equally repre- 

 sent differences of age and origin. 



To designate those geographic groups, made in accord- 

 ance with present peculiarities of distribution, as so many 

 distinct " floras," seems only a premature misuse of this 

 term. — The species cannot be held to constitute distinct 

 floras by geographical or topographical position, because 

 they constantly intermingle; so much so, that not a 

 single province among the whole eighteen can be named, 

 in which less than three of the six types occur ; while 

 four or even five of them are represented (by some of 

 their species) in many of the provinces. — The species 

 cannot be held to constitute distinct floras botanically, 

 because no peculiarities of structure or classification have 

 been shown to characterize any of the types, other than 

 such as are usually traceable in relation to existing cli- 

 mate in its connexions with diff"erence of elevation, lati- 

 tude, &c. — The species cannot be held to constitute 

 distinct floras by duration, because no evidence is yet 

 forthcoming, at all adequate to show which species of the 

 indigenous flora have been the longest time in Britain, or 

 are the oldest by their whole existence, if these are not 

 coeval durations. 



In reference to this last ground of objection, it ought 

 to be clearly understood by geologists and others inte- 

 rested in the matter, that not the slightest botanical evi- 

 dence has hitherto been adduced, on which to found a 

 belief, that the types of distribution here treated about 

 are in anywise connected with the comparative ages of 

 the species assigned to them. No botanical facts are 

 known, such as can warrant an assertion that any one of 



