4 MR JOHN MACRAE ON THE FLORAS 
there is Lamiwm maculatum, which has quite established 
itself beyond Dalkeith, and is, Mr Brock informs me, by no 
means rare in Linlithgowshire. 
It would seem not only that in more populous country 
districts man has a better opportunity of influencing the 
Flora, but also that the outward conditions are themselves 
more favourable to the development of plant-life. 
It would not be idle to inquire into the reasons of this. 
First, we may note the fertility of the soil. It is, on the face 
of it, likely that the richer soil would have the richer and 
more diversified Flora. But here man may add a factor to 
it, and I think he has, in the enrichment. You have the 
West mainly Celtic in origin; the East mainly Teuton. Now 
the Teutons occupied themselves in diligently tilling the 
soil, but the Celts went in far more for pasturage; this 
would give a dim historical background to the fact that 
weeds of cultivation in the West are fewer than in the East, 
but it could not, in any case, be a seriously determining 
factor, 
Other geological conditions, eg., the comparative rockiness 
of, say, Cantire, would account for something, and the 
geological formations have no doubt much to do with the 
fertility of soil. 
The present geographical position brings still more light 
on the subject. For one thing, the East is nearer to the 
main body of Britain than is the West—the Solway Firth 
does much to interrupt continuity, while the Cheviots do very 
little. And the comparative nearness of the East Coast of 
Britain to Europe makes its influence by Continental Flora the 
more certain; perhaps persisting from pre-North Sea times ; 
perhaps seeds carried across by birds in their annual migra- 
tions. This may help to explain the persistence of forms 
—eg., the Alliums and Caucalis nodosa—to a higher latitude 
in the East than in the West on the borders of the Old 
World. 
But the main determining factor, I think, is climate. 
The West is warmer than the East in winter—as I can 
testify from experience—but colder in summer; but the 
equableness of temperature seems to have little effect on 
floral richness or the contrary. What does have effect is 
