THE CLIMA TE OF IRELAND. 249 



wheat crop of 1864 ripened well with only the 

 average temperature of 54'4°. In that year, how- 

 ever, the sunshine was much above the average, and 

 the mean of the daily maximum temperature was 

 high, being as high as in August 1861, when the 

 mean temperature was 57'4°. 



" It is probable that the longer time the sun is 

 above the horizon in Scotland, as compared with 

 Germany and France, renders the ripening of this 

 cereal possible with a lower mean temperature, and 

 when this is combined with a clear dry atmosphere, 

 and consequently a blazing, scorching sunshine, grain 

 of excellent quality is ripened, though the mean 

 temperature rise no higher than 54'4°. From this 

 it is clear that in regarding the influence of temper- 

 ature on bringing plants to maturity, it is not mean 

 temperature merely, but the way in which the vital 

 element is distributed through the day and night, 

 particularly at the critical periods of the plants' 

 growth, which must be considered. A high mean 

 temperature, with little variation, implies a compara- 

 tively low day temperature ; and, on the other hand, 

 a moderately low mean temperature, with a large 

 daily range, implies a high day temperature ; so that 

 a climate with a comparatively low mean temperature 

 may yet afford the warmth required in carrying on the 

 higher functions of the plant which another climate 

 of a higher mean temperature could not supply. 



" Now, that which in the highest degree deter- 



