Night Temperature in hothouses and frames should always ave- I rage from 10 to 20 degrees lower than the temperature in which the plants are grown during the day. It is in the night that the individual functions are renovated by a temporary repose, and if left to the dictates of healthy nature, the sap, like the blood, flows at night, with a much diminished velocity.

That plants do become exhausted by too unremitting excitement, is proved to every gardener who has peach-houses under his rule ; for if the greatest care be not taken to ripen the wood by exposure to the air and light during the summer, no peach tree will be fruitful if forced during a second successive winter, but will require a much more increased temperature than at first to excite it even to any advance in vegetation.

The experiments of Harting and Munter upon vines growing in the open air, and those of Dr. Lindley upon vines in a hot-house, coincide in testifying that this tree grows most during the less light and cooler hours of the twenty-four. But the hours of total darkness were the period when the vine grew slowest. This, observes Dr. Lindley, seems to show the danger of employing a high night temperature, 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 temperature not higher than 50°, inhales from one-sixteenth to one-tenth less oxygen than a similar branch of the same vine during the same night in a temperature of 75°. The exhalation of moisture and carbonic acid is proportionably increased by the higher temperature.-Principles of Gardening.