H. BOTANY AND HORTICULTURE. 297 



its color, during the electrization of the leaf, becoming grad- 

 ually infiltrated toward the upper green surface, so as to 

 mask the color of the chlorop*hyl. He farther remarks that 

 the atmosphere and the earth are constantly in two dissimi- 

 lar electrical conditions, the first possessing an excess of pos- 

 itive electricity, the second of negative, these two excesses 

 becoming neutralized by means of the conducting substances 

 found at the surface of the earth, plants especially. 3 JE>, xn., 

 July 20, 660. 



WATERING PLANTS W T ITH HOT WATER. 



It.has been shown, by careful experiment, that sickly pot- 

 ted plants, even some that have almost died out, can be 

 greatly benefited, and sometimes, indeed, entirely restored to 

 vigor, by applying warm w r ater to them instead of cold. In 

 certain cases, oleanders which had never bloomed, or did so 

 only imperfectly, after being treated with lukewarm water, 

 increasing the temperature gradual^ from 140 up to 170 

 Fahr., produced the most magnificent luxuriance of bloom. 

 Similar results occurred with an old plant of Hoya, and also 

 with an India-rubber-tree which had nearly withered away. 

 In all these cases the application of water heated to about 

 110 Fahr., without any other precaution, caused a new and 

 flourishing growth. 8 C, December 8, 1870,391. 



INFLUENCE OF CONDITIONS OF HEAT ON THE GROWTH OF 



PLANTS. 



A paper has'been published by Koppen upon the relation- 

 ship of conditions of heat to the phenomena of growth in 

 plants, his first inquiry being limited to the questions con- 

 nected with the germination of the seed. The general con- 

 clusion arrived at was that variations of temperature were in 

 all cases prejudicial to the growth of the germ, even when 

 amounting to but a few degrees, and these within limits fa- 

 vorable to energetic growth ; that is to say, the germination 

 proceeds more rapidly at a low temperature of a xmiform. de- 

 gree than at a higher w T here subjected to more or less varia- 

 tion. From this we derive the inference that a nearly uni- 

 form spring temperature, with a cloudy sky, is more favorable 

 to rapid development of vegetation than the alternation of 



hot days and cool nights, it being of course understood that 



N2 



