The Garden Under Glass

262 THE GARDEN UNDER GLASS Ventilating a Plant House There is a decided difference in the ventilating of a fruit house and a plant house, or even that of a hot or a cold house. It is, of course, impossible to give such precise precepts that any novice may undertake to ventilate a house as well as if he had undergone years of experience. The most that can be done with the pen is to show some faults to avoid and to indicate the general principle of ventilation. As much air should be afforded as possible without letting the temperature drop lower than the figure which is known to be the minimum, with this leservation that during bright days the thermometer may safely stand io° higher than on duli days and at nights. For instance, it is well known that the temperature of stove plants should range between 65° and 70°. This is the night and the normal figure. With the sun striking upon the house the temperature will rapidly rise. When the glass stands at 750 some air should be afforded at the apex of the house —just a little. If it rises still higher the vents may be more widely opened, and. the endeavour should then be to keep the house in the neighbourhood of 8o°. During duli spells it will be necessary to diminish or entirely take off the ventilation to prevent sharp fluctuations of temperature. Early in the afternoon the house may be shut up entirely so cis to bottlc up some of the sun-heat, and thus render the use of the fire-heat needless until the night. To counteract the drying and scorching influence of thus closing a house during füll sunshine the plants are freely syringed, and. all available surfaces are damped, so as to flood the atmosphere with moisture. The ventilation of a cool house, of course, is worked on a different principle. To maintain the necessary tempera-