INTRODUCTION 3 
divided owing to its configuration and the relation of 
its axis and movements to the sun, the source of heat, 
and of temperature, winds and rain. 
But one may locally consider that the north differs 
from the south, the west from the east. This is 
reflected, in fact, in the flowering seasons of the 
same plant at the extremities of these islands north 
and south. 
The north is much colder relatively than the 
south, owing to latitude ; the west much moister than 
the east owing to the influence of the Atlantic and 
the Gulf Stream. 
So that we may distinguish different types of 
plants in the north, as defined by Watson, Scottish 
plants, and in the south English types, whilst in the 
west we have Atlantic types, and in the east Germanic 
types. These different types depend upon other 
factors, but climate is also largely responsible for the 
differences in the plants in the north, south, west, 
and east of the British Isles. 
Next to the influence of climate comes that of 
altitude, which has a result similar to the former, 
caused by the greater cold as one travels from south 
to north, whereas in this case the heat decreases as 
one ascends vertically. 
The hills and mountains in this country do not 
exceed 4000 ft., so that the contrast is not so marked 
here as on the Continent, where the altitude is 
15,000 ft. or over, and alpine plants flourish on the 
summits. 
