Perthshire in Relation to ‘ Age and Area' . 32 3 
in the search for a solution to the much-debated problem of the origin and 
distribution of the British flora as a whole. 
So far as Perthshire is concerned, the following quotation from White’s 
‘ Flora ’ ( 1898 ) gives fair expression to the problem : ‘ I have been speaking 
of the British flora and Britain, but with the object of attempting to show 
that what concerned these in remote ages may have a more modern 
application to the Perthshire flora and to Perthshire. The various con- 
trivances for the dispersion of plants, to which we have alluded, clearly 
indicate that the extension of the area of plants is for the benefit of the 
species. Perthshire is not cut off by the sea from the rest of Britain, 
therefore the methods by which the British flora reached Britain, when 
there was a land connexion, may have always been, and still be, operative 
as regards Perthshire in relation to the rest of Britain provided that 
climatic conditions are favourable, and that there is room.’ It is clear 
that Dr. White held the view so consistently advocated by Mr. Clement 
Reid regarding the destruction of Britain’s pre-glacial flora during the 
period of maximum glaciation, and on this view, that the Perthshire flora 
re-immigrated during post-glacial times, we may, without lengthy discussion 
on a debated question, proceed to examine the facts of present dis- 
tribution. 
There are 738 flowering plants admitted as ‘ native species ’ in the 
county, and their range of distribution, in terms of the number of districts 
they occupy, is shown in the following table : 
Table I. 
Occupying. 
Number of 
species in 
Perthshire. 
Percentage. 
Same species 
in Britain. 
Percentage. 
I. 
Thirteen districts 
190 
2 5-7 
2 58 
35-o 
2 . 
Twelve 
33 
US 
15-3 
72 
9.8 
3- 
Eleven 
33 
42 
5*7 
77 
10.4 
4- 
Ten 
33 
30 
(pf 4 ' 1 
52 
7-i 
5- 
Nine 
*3 
34 
Xr 4.6 
58 
7-9 
6 . 
Eight 
33 
35 
4.7 
29 
3-9 
7- 
Seven 
?3 
4 1 
5.6 
30 
4.1 
8 . 
Six 
33 
36 
4.9 
18 
2.4 
9- 
Five 
>3 
27 
3-7 
18 
2.4 
10 . 
Four 
33 
3i 
4.2 
32 
4*3 
11 . 
Three 
33 
43 
5*8 
3i 
4.2 
12 . 
Two 
33 
41 
5.6 
28 
3-8 
i3- 
One district 
75 
10. 1 
35 
4-7 
If we mark the rarity of these groups from one to thirteen simply, to 
awkward fractions, the average rarity for the total number of species 
^ ^ for same species in Britain, calculated on the same basis 
is 5-6, dis* 
vice-corn^ 1 
^ 'butional data, the rarity is 4*4. Thus, within the 
frotn p el . t hshh e > specie^ are, on the average, not so widely distributed 
\\mhs 0 potato- *■ , right be expected from general considerations 
as they fiscal position. WV graphic, climatic, and edaphic factors. But 
of g e0gva1? 
