364 RESTING VEGETATION. 



cold and late soils and situations, and brought to earlier ones, continue 

 for a time to be late from habit, and the contrary ; and hence the 

 practice of farmers in cold, late districts procuring their seed-corn and 

 potato-sets from low, warm districts, and the contrary. When plants 

 are grown in pots, they can generally be more effectually either accele- 

 rated or retarded than by any other means ; because they may be at 

 pleasure transferred to a cold cellar, to an ice-house, or to a forcing- 

 house. Thus fruit trees and flowering shrubs in pots, put into an ice- 

 house in January, will have their vegetation retarded for any length 

 of time, as no growth can take place where the temperature is under 

 the freezing point. Plants so treated, if not retained too long, may be 

 made to vegetate at any season that is desired, but the transition from 

 the temperature of the ice-house to summer-heat must be very gradual, 

 in order that the buds may be fully distended with sap before they are 

 developed. Fruit or vegetables which would spoil or advance too far 

 if left on the plants, such as peas, cauliflowers, cucumbers, peaches, 

 &c., may be retained several days in the state required in the ice- 

 house, or in a room adjoining it, and even for a certain period in a 

 cool cellar or shed. The earliest potatoes are obtained by some gar- 

 deners by keeping them in a place so cool as to prevent vegetation for 

 two seasons : that is, the produce of the summer of one year is to be 

 planted in the December of the year following. The German gardeners, 

 by retarding the roots of the ranunculus in this manner, are enabled to 

 produce it in flower all the year, and the same thing might be effected 

 with various bulbs. The flowering of annual plants is easily retarded 

 by sowing them late in the year ; and on this principle the gaiety of 

 the flower-garden is preserved in autumn, and culinary productions, 

 such as spinach, lettuce, &c., obtained throughout winter. 



Resting Vegetation. 



In the natural state of vegetation all plants experience a more or less 

 low degree of temperature during the night than during the day. In 

 the tropics the difference is but little, particularly as regards plants 

 that grow in the shade. It, however, increases from the torrid to the 

 frigid zone ; and therefore artificial temperature should be regulated 

 accordingly. Tropical plants are injured by a greater discrepancy of 

 temperature than occurs in their native regions. There the tempera- 

 ture independent of direct sun heat is almost uniform. But in the 

 case of such plants as the vine, the fig, and the peach, the natural 

 habit of which extends to a latitude as high as 45, a considerable 

 range of temperature is necessary. They enjoy, in summer, a long 

 day of high temperature indeed, a tropical heat ; but at night a 

 tropical temperature is not maintained. These plants, and others 

 having corresponding habitats, require not only a temperature lower 

 by night than by day, but also lower in winter than in summer. 

 Tropical plants, on the contrary, are injured by having a wintering 

 imposed upon them, a condition they are never naturally placed in. 

 In particular situations, even in extra-tropical countries, plants may be 



