164 PRINCIPLES OF GARDENING. [CH. V. 



trees to be subjected to a freezing tem2:»erature. It 

 v,il\ be found, generally, that the forced tree that is 

 kept longest vegetating healthily after its finiit is 

 gathered, \\ill be the most vigorous next season. 



The experiments of Hai'ting and Munter upon 

 \ines growing in the open air, and those of Dr. 

 Lindley upon \dnes in a hothouse, coincide in testi- 

 fying that this tree grows most duiing the less light 

 and cooler houi's of the twenty-four. But the hours 

 of total darkness were the period when the vine 

 grew slowest. This, observ^es Dr. Lindley, seems 

 to show the danger of employing a high night tem- 

 perature, which forces such plants into growing fast 

 at a time when nature bids them repose ^. 



That the elevation of temperature at night does 

 hurtfully excite plants, is proved by the fact, that 

 the branch of a vine kept at that period of the day 

 in a temperature not higher than 50'', inhales from 

 one-sixteenth to one-tenth less oxygen than a simi- 

 lar branch of the same vine during the same night 

 in a temperature of 16°. The exlialation of mois- 

 ture and carbonic acid is proportionably increased by 

 the higher temperature. 



The e^■idence of the vine's growth being most 



rapid during the hours of diminished light, but not 



of entire darkness, is curiously coincident with the 



observation of Moses, that, though fruit is brought 



^ Hort, Trans. 109. 



