FREAKS OF PLANT LIFE. 371 



CHAPTER XVII. 



TEMPERATURE, 



Without concerning ourselves greatly as to the 

 general temperature of plants, we may premise that 

 the accepted opinion is in favour of the conclusion 

 that it is more equable than that of the surrounding 

 air; that at night, or in winter, it is above, and in mid- 

 day, or in summer, it is below the atmospheric tem- 

 perature. Most of those who have made experiments 

 have come to the conclusion that trees with thick 

 trunks have a temperature lower than that of the 

 air during great heat, and higher during extreme 

 cold. Dr. Hooker made some observations in India, 

 and was of opinion that the temperature of the fluids 

 in a plant coincided ^\■ith that of the soil at the spot 

 whence the largest absorption was derived. That a 

 shaddock fruit maintained the same temperature 

 at mid-day with the atmosphere at 110°, as at mid- 

 night with the thermometer at 68°. He remarked 

 that, " when the surface sand in the Soanc Valley 

 was heated to 110° the fresh juice of Calotropis plant 

 was only 72'. This latter temperature he found at 

 fifteen inches depth in the soil where the plant grew. 

 The power which the plant has in maintaining a low 

 2 B 2 



