82 VITAL ACTIONS. 



witli thin leaves, long joints, slender stems, and vriih 

 no disposition to produce flowers. A slight lowering 

 of temperature affects them more than a much greater 

 lowering would have done under other circumstances ; 

 and a permanent abstraction of light readily destroys 

 them. Their inability to decompose carbonic acid, 

 and to assimilate their food in proportion to their 

 rate of growth, prevents their becoming so green as 

 is natural to them, and gives them a pallid hue ; and, 

 if it is their property to secrete other colouring mat- 

 ter, that, like all their other secretions, is greatly 

 diminished. But if, with a preternatural elevation 

 of temperature, there is a proportionate abstraction of 

 moisture, the loss of fluid, by perspiration and evapo- 

 ration, goes on faster than the roots can make it 

 good, or the tissue transmit it ; the secretions of the 

 species are elaborated faster than the parts to receive 



perature is to cause, in unisexual plants, the production of male 

 flowers only, while a yery low temperature produces the contrary 

 result. A Water Melon plant was grown in a house, the heat of 

 which was sometimes raised to 110° during the middle of warm and 

 bright days, and which generally varied, in sucli days, from 90° 

 to 105° declining during the cTening to about 80°, and to 70° in the 

 night ; the air was kept damp by copious sprinkling with water, of 

 nearly the temperature of the external air, and little ventilation 

 was allowed. The plant, under these circumstances, grew with 

 great health and luxuriance, and afforded a most abundant blossom ; 

 but all its flowers were male. "This result," he says, "did not, in 

 any degree, surprise me ; for I had many years previously suc- 

 ceeded, by long-continued very low temperature, in making Cucum- 

 ber plants produce female flowers only ; and I entertain but little 

 doubt that the same fruit-stalks might be made, in this and the pre- 

 ceding species, to support either male or female flowers in obedience 

 to external causes." (Jlort. Tran^ vol. iii. p. 460.) 



