OF THE ATMOSPHERE OF HOT-HOUSES. 327 



tant phenomenon, of universal occurrence, and that it takes place 

 equally in the hottest and in the coldest regions. It is, there- 

 fore, a condition necessary to the well-being of a plant, not to 

 be overworked, under any circumstances whatever ; and there 

 cannot be any good gardening where this is not attended to, in 

 the management of plants under glass. Rest is effected in two 

 ways ; either by a very considerable lowering of temperature, 

 or by a degree of dryness under which vegetation cannot be 

 sustained. 



In treating on the various conditions of the atmosphere, and 

 its effects on vegetation, we have already sufficiently explained 

 these influences ; which renders it unnecessary to recapitulate 

 them in this place. In practice we find that the effects of a 

 very dry atmosphere are, necessarily, an inspissated state of the 

 sap of the plant, and this, in all cases, if not carried to an 

 injurious extent, leads to the formation of blossom-buds, and 

 of fruit. This influence, however, must be controlled by the 

 cultivator, otherwise it will lead to inevitable failure, as the sap 

 of the plant may be so much dried up as to prevent its accumu- 

 lation in sufficient quantity, in the smaller branches, to form 

 fruit buds. It is, nevertheless, true, that a low temperature, 

 under the influence of much light, by retarding and diminishing 

 the expenditure of the sap in growing plants, produces nearly 

 similar effects, and causes an early appearance of fruit. 



All the operations may be very essentially influenced by these 

 facts, when they are fully understood to the cultivator, and, by 

 a skilful alteration of the periods of rest, we are enabled to 

 break in upon the natural habits of plants, and to invert them 

 so completely, that the flowers and fruits of summer may be 

 brought to perfection at the opposite season of the year. 



By carrying out these principles, we have, for several years, 

 succeeded in fruiting grape-vines in the months of March and 

 April, without any extraordinary degree of excitability being 

 exercised at any period of their growth. The whole secret of 

 success consists in preparing the plants the preceding season, 

 by ripening their wood at an early period of the season, and ex- 

 posing them to such an amount of heat and dryness as can be ob- 

 tained by presenting them, unwatered, to the influence of the sun, 



