170 PAST AND PRESENT 
Southern Europe, but from Scandinavia most are 
absent, and the rest are rare. On the other hand, 
some characteristic Scottish species cease aS we come 
southward—the little Primula scotica, for instance, 
is confined to the northern extremity of Scotland; the 
Chickweed Wintergreen (Trientalis europea) ranges 
only as far south as Yorkshire; and the beautiful 
Globe Flower (Trollius europeus), so characteristic 
of northern pastures, creeps southward as far as the 
Severn. The first of these is on the Continent con- 
fined to Scandinavia; the others, though found in 
France, etc., are characteristic of the hilly regions 
there, and are much more abundant farther north- 
ward. 
Next to this north-and-south change, due to 
climate, we may notice an east-and-west change, due 
partly to climate, but more perhaps to elimination, 
for in passing from France to Ireland we have to cross 
two barriers of sea. The climatic change is not 
unlike that experienced in going from south to north. 
We leave a dry climate (rainfall under 25 inches a 
year) for one of increasing wetness, a warm for a 
cool summer, a colder for a milder winter. 
The chief difference between the extreme west of 
the British Isles and the extreme north lies in the 
warmer winter of the former, frost being almost 
unknown in the milder spots. But the general simi- 
larity of northern and western conditions as opposed 
to eastern and southern leads to a fusing of the 
northern and western plant groups, so that on a map 
designed to show the distribution of our species 
analyzed according to their general range in Europe, 
the grouping of plants in the British Isles will be 
