248 THE GARDENER. [June 



Exotic flowers and fruits in forcing-houses and pits are in circum- 

 stances so thoroughly artificial in respect to two such important 

 conditions as those of heat and air, that the appliances which are 

 necessary to regulate these conditions are the very sources from which 

 danger and harm to delicate plants arise. It is not possible by any 

 known means to produce and regulate that amount of warmth 

 required by exotic plants of the most tender description, without 

 enclosing a volume of air in a transparent glass house, and heating it 

 by artificial means, in order to compete with the rigorous variableness 

 of our climate. True, at certain short intervals we could, as it were, 

 entrap within the limits of our glass cases as much or even more heat 

 for a short time than is required ; but even in the height of our best 

 summers this would be most uncertain and fitful, and therefore the aid 

 of fire-heat, unnatural as it is, becomes indispensable. Yet it is from 

 the proper use or balancing of these two sources of heat that the most 

 thoroughly satisfactory results, in what is generally termed forcing, to a 

 very great extent depend. The more sun-heat that can be made avail- 

 able, and the less fire-heat that is made use of to keep up temperature 

 to a proper degree, the better is it for the wellbeing of plants, and 

 vice versa. Of course the horticulturist has no control over clouds and 

 sunshine ; nevertheless he can very efi'ectively store up the sunbeams, 

 and save his coals, while he is at the same time doing the very best 

 on this point for his crops. It is well known to all experienced 

 cultivators how much better plants thrive when he can command his 

 maximum temperature with a minimum or entire absence of tire-heat. 

 It is equally well known how injurious it is to have these two sources 

 of heat in vigorous activity at the same time, and how, at certain 

 seasons especially, it is most difficult to hold the one in proper 

 abeyance while the other does the work. True, with a well-constructed 

 hothouse and an efficient heating apparatus, heat under certain cir- 

 cumstances can be measured out to the atmosphere almost to a 

 degree ; but capricious sunshine outwits the most careful calculations 

 and management of the fireman ; and we are far from envying the 

 person who is placed between a hot fire, a hot sun, and a hot-tempered 

 superintendent all of a sudden ! 



How often, after a cold night and a still colder dawn in April, is it 

 not found necessary to add a little coal and stimulus to the fire, in 

 order tp prevent a sudden and injurious depression of temperature ! 

 and presently the sun suddenly and unexpectedly throws his power 

 into the scale with hot pipes, and we have a combination the most 

 undesirable and injurious. To counteract the evil efi'ects of a parch- 

 ing heat, the fire and ventilating apparatus call for immediate atten- 

 tion. The one must be smothered up and beaten down firmly, &c., 



