232 PLANTS ADJUSTING THEIR OWN TEMPERATURES. 



it is evident that one of their most agreeable qualities 

 would be gone. Yet, as we know, many of these fruits 

 only attain their full perfection, when exposed throughout 

 the day to the scorching rays of a vertical sun. To 

 what therefore are we to attribute this curious and 

 beneficent peculiarity? A Water Melon (Cucurbita 

 Citrullus, or Red-fleshed water melon) for instance, 

 growing in a river bed, upon an expanse of sand, 

 from which the waters have retired, if eaten immediately 

 after being severed from the plant, will appear almost 

 as cold as if iced and yet the sand upon which it 

 rested, may have become so superheated by the sun, 

 that it will burn the naked hand if it comes in con- 

 tact with it. It will be found that this characteristic 

 in various degrees, is more or less common to every 

 species of fruit. 



This is surely a most remarkable and surprising 

 fact, by which we have all, from time to time, profited; 

 but while experiencing a grateful sense of its pleasant 

 refreshment, it has very likely occurred to but few of 

 us to ask ourselves, Why is it so? yet few natural 

 phenomena are more curious, or better deserving of 

 our attention, than this marvellous power of plants of 

 maintaining and adjusting their own temperatures. 



In cold climates, for example, it has been found 

 that the temperature of vegetables is usually somewhat 

 higher than that of the atmosphere ; but in hot climates 

 it is maintained at a point considerably below it; and 

 although the causes of this singular faculty appear to 

 be as yet somewhat imperfectly understood, it seems 

 probable that the coolness of fruits is simply the 

 result of evaporation, consequent upon the power 

 possessed by the roots of plants, of constantly attracting 



