/ 
' 
Perthshire in Relation to 'Age and A rea \ 327 
of those plants which were directly or indirectly affected by human 
activity. Thus, the mass of the flora, a recent temperate assemblage, fits in, 
generally speaking, with the ideas expressed in the ‘ Age and Area’ theory. 
Since the Highland plants are relics, their range will not depend upon age 
but upon other factors, and their curve of distribution may be, and in 
Britain is likely to be, irregular. The curve for the species in Perthshire 
is shown in Fig. 2, and above it is placed the curve for the temperate or 
general lowland flora. Further comparisons between the outgoing and 
incoming floras suggest themselves, but these are left for another paper 
which will deal with the entire Scottish flora. 
Summary. 
The native flowering plants in Perthshire number 738, of which 605 
(or 82 per cent.) belong to a lowland or temperate flora. This element is 
concentrated in the Lowland districts of the county and thins out in the 
Highland districts. The distributional data relating to these species, 
arranged according to number of districts occupied, furnish evidence to 
show that the general principle expressed in the recent theory of distribution 
termed ‘ Age and Area ’ is applicable to a county flora. Exception to the 
general bearing of the hypothesis is not unexpectedly found in the dis- 
tribution of the remaining 133 species, which are essentially arctic-alpine or 
boreal plants. These, as proved by the fossil record, are relics of a northern 
flora formerly more widespread, and a gradual elimination since glacial 
times has produced their present discontinuity of distribution. 
Literature cited. 
Bennie, J. (1896) : Arctic Plant Beds in Scotland. Ann. Scot. Nat. Hist. 
Chandler, M. E. J. (1921) : The Arctic Flora of the Cam Valley. Quart. Journ. Geol. Soc., 
lxxvii, Pt. I. 
Lewis, F. J. (1911) : The Plant Remains in the Scottish Peat Mosses. Trans. Roy. Soc. Edin., 
xlvii, Pt. IV. 
Reid, C. (1911) : On the Relation of the present Plant Population of the British Isles to the Glacial 
Period. British Association Report : Portsmouth Meeting. 
White, F. B. (1898) : The Flora of Perthshire. 
Willis, J. C. (1915) : The Endemic Flora of Ceylon. Phil. Trans., B., ccvi. 
(1920) : Plant Invasions of New Zealand. Ann. Bot., xxxiv. 
r (1921) : Endemic Genera of Plants in their Relation to others. Ibid., xxxv. 
an( j YULE, G. U. (1922) : Some Statistics of Evolution and Geographical Distribution 
in Plants and Animals. Nature, cix. 177 . 
