Climatal Influences. 565 
enjoy the delights of luxuriant verdure all through the heat of 
summer; whereas in many other parts of Europe vegetation 
is scorched up. The disadvantages are also important, espe- 
cially a deficiency of solar heat for the maturation of fruits 
and seeds of many plants. There is a great divergence in 
the direction of the isothermal lines in summer and winter 
for the British Isles. The general direction of the summer 
lines is from west by south to east by north, with a slightly 
higher temperature inland in the centre and south of England ; 
whilst the winter lines run nearly parallel with the east and west 
coasts. The mean summer temperature ranges from 63° or 64° 
in the south of England to 55° or 56° in the north of Scotland ; 
and the mean winter temperature ranges from 37° on the eastern 
coast and inland, to 39° on the north-west and south-east 
coasts, and upwards to 43° or 44° in the south-west. But winter 
extremes, more than winter means, affect the gardener; and 
when the thermometer falls below zero the frost is very destruc- 
tive. In round numbers, the mean annual temperature of the 
British Islesis about 50°, but it varies in different localities from 
53°to 47°. The higher summer temperature of the east and 
centre raisesthe mean annual temperature considerably ; but the 
difference of siz or seven degrees in the mean winter tempera- 
ture of different parts of Britain and Ireland, to say nothing of 
extreme degrees of cold, goes farther to determine the question 
whether certain plants can be grown in the open air without 
or with only slight protection in winter. Although the mild 
and comparatively equable climate of the south-west of Eng- 
land and the south of Ireland is favourable to the existence 
of tender subjects such as will not withstand the climate of 
the centre and east, the higher summer temperature of the 
last-named region, coupled with less rainfall and more sunlight, 
is of far more importance to the fruit and seed grower. Many 
plants that flower freely in the moist uniform climate of the 
south-west do not ripen their fruits; whereas the more con- 
tinental summer of the centre and south-east is sufficient to 
bring them to maturity. There is a still greater disparity in 
the average annual amount of rain falling in different parts 
of the British Isles. The greatest fall is in Ireland and on the 
western coast of Britain in mountainous districts, gradually 
diminishing eastward, and reaching its minimum in the south- 
eastern counties. The average annual rainfall in Ireland and 
hilly regions in the west of Britain ranges from 80 tv 150 
