CFnnatal 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 Isles is about 50, but it varies in different localities from 

 5 3 to 47. The higher summer temperature of the east and 

 centre raises the mean annual temperature considerably ; but the 

 difference of six 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 to 150 



