318 VII. AREAS OF SPECIES. 



south ; for instance, Lijeopodium Selago and Genliana campestris (page 

 305). 



The subdivisions of the list of general species are sufficiently ex- 

 plained bj- the head-titles of the subordinate groups. Within each of 

 these latter groups, the series or succession of names is determined by 

 the number of sub-provinces ascertained for the several species ; with 

 the exception of the first, in which their comital extension northward is 

 also taken into account. Thus, in the group of plants ascertained in all 

 the provinces, and in latitude 50 — 59, are the following, with others 

 intermediately placed : — Filago minima (31 sub-provinces), Lislera uvata 

 (33), Ononis arvensis (35). And among the plants which extend to 

 Orkney, the following succession occurs : — Mentha aquatica (34), Vero- 

 nica scutellata (35), Peplis Portula (36), Arenaria serpylUfolia (37). 



Boreal and Montane Species. — The third divisional list (page 305) may 

 be considered the reverse of the first; the plants therein included 

 attenuating, or successively decreasing and ceasing, in a direction from 

 north to south. Or, virtually the same fact, they are species which are 

 scarce or unknown in the low southern provinces of England ; first 

 appearing, or else increasing in frequency, as an observer of them 

 advances from those provinces into others more northerly or more 

 mountainous. The tendency of many of these plants to a northerly 

 prevalence, including several of those which are quite restricted to the 

 comparatively northern latitudes, is closely connected with the moun- 

 tainous and moorish character of the surface there, and less directly 

 with the latitude of itself Many do not occur at all to the northward 

 of the Grampian Mountains, situate between latitudes 56 — 58 ; while 

 some of them are so little boreal, with respect to total Britain, as to be 

 exclusely limited to Mid Britain; one even to South Britain. But 

 these English plants are still taken along with the boreal plants, be- 

 cause they are found only or chiefly about the mountains; associated 

 with others which severally extend more and more to the northward, 

 and in such a gradual manner as to render impracticable any decided 

 line of distinction between the boreal and montane plants. Thus it 

 happens that the Lloydia serolina, of Carnarvonshire, is classed with the 

 montane and boreal plants, because found only at a considerable eleva- 

 tion ; while the Cotoneaster vulgaris, of the same county, was enume- 

 rated among the austral plants, because found there only on the coast 

 rocks, at a slight elevation compared with that of the former plant. So, 



i 



