Species may be synoical at all stages of relationship. We come across varieties, scarcely distinguishable from one another, growing in the same locality (as, for example, the _Cirsium heterophyllum_, with smooth or jagged leaves, the _Hieracium 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. holadenium_, 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 (_A_ to _I_). _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 (_Rothwand_) 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 intermediary 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 distinguishable 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.