Evidences of Physiological Selection. 83 



growing in the same locality (as, for example, the Cirsium 

 heterophyllum, with smooth or jagged leaves, the Hieraciutn 

 sylvaticum, with or without caulinary leaves) ; again, we meet 

 other varieties more accentuated (as the H. hoppeanum, with 

 under ligules of white or red, the Campanula, with white or lilac 

 flowers, &c.), other varieties even more marked, which might 

 almost be elevated to the rank of species {Hieracium alpinum, 

 with hairs and glands, and the new form H. holadeniuin, which 

 has only glands. Campanula rotundifolia with smooth and hairy 

 leaves), or forms still more distinct, up to well-defined species. 

 I could enumerate endless examples at all stages. 



It will be seen that in my definition of synoicy I do not mean 

 to assert that all allied forms are invariably found together, but 

 that they are much more often seen in groups than singly. 

 Take, for instance, nine forms closely related (^ to /). A, E, H 

 will be found side by side at one point, B, D at another, C, F 

 at a third, &c. These facts are plainly opposed to the theory of 

 isolation and amixia, and make, on the contrary, in favour of the 

 social development of species {loc. cit., p. 221). 



Not to multiply quotations to the same general effect, 

 I will supply but one other, referring to a particular 

 case. 



At one spot (Rotkwand) much exposed to the sun, and 

 difficult of access, I remarked two closely allied forms, so nearly 

 related to H. villosum that this would seem to be an interme- 

 diary form between the two. One of these {H. villosissimum) 

 is distinguished by its tongue and thick pubescence, its tolerably 

 large capitula, and by the lengthened and separated scales of 

 the involucrum ; the other, on the contrary {H. elongatum), is 

 less pubescent, has smaller capitula, and more compact scales 

 on the involucrum than H. villosum. Both are finally distin- 

 guishable from the type by their longer stalks, which are more 

 decidedly aphyllous, and by their later flowering. At the spot 

 where I found them the two forms were closely intermingled, 

 and each was represented by a considerable number of plants. 

 I did not find them anywhere else on the mountain, nor could 

 I find at the spot where these were growing a single specimen 

 of the true H. villosum, nor a single hybrid from these two. 



G 3 



