XII. TYPES OF DISTEIBUTION. 501 



qually among the provinces, besides the successive cessa- 

 tion from south to north, and from north to south. Thus, 

 in the list of ' boreal and montane species ' there is an 

 evident tendency or entire restriction among many of 

 them to the most mountainous provinces — 15, or 15 16 17, 

 or 7 - - 10 11 12 - - 15 16 17 18 — while no such 

 special tendency can be detected in others. This is con- 

 nected with the double character of the group, implied in 

 the title, and mentioned on page 318. The whole group 

 is subdivisible into northern species and mountain spe- 

 cies ; although these two secondary groups really pass so 

 gradually one into the other, as not to admit of any clear 

 line of severance. Further, it may be observed that some 

 of these plants terminate northward in provinces 10 or 13, 

 more rarely in 11 or 14 ; not attaining the Highland pro- 

 vinces. There is thus seen to be a small group among 

 the boreal and montane plants, composed of species which 

 are restricted to the middle j)rovinces, or else to the mid- 

 dle and some of the southern provinces; shunning those of 

 North Britain. The differences here mentioned suggest 

 a sub- division of the boreal and montane group, regarded 

 as a whole, into Highland, Scottish, and Intermediate 

 types ; including with the latter some few mid-British 

 plants which do attain the East Highland province. 



Beverting to the list of ' austral species,' especially to 

 its earlier sub-divisions including those plants which ter- 

 minate southward of latitude 53 or 54, it will be noted 

 that several of them occur only or chiefly in the easterly 

 provinces — 3, 4, 3 4, 3 3 4; others occurring only or 

 chiefly in the westerly provinces — 1 5 G 7 — some or all 

 of these ; and the rest being found about equally diffused 

 in both eastern and western provinces, as shown by the 

 figures, and by the vowels indicating their longitudinal 

 ranges. This tendency to one or other side of the island 



