SECTION li. 



EFFECTS OF VENTILATION, &C. 



1. The ventilation of hot-houses, during winter, requires all 

 the skill which the most experienced gardener has at command. 

 It is a comparatively easy matter to open and shut the sashes, or 

 ventilators ; but to do so with benefit to the plants, at all times, 

 requires an amount of skill which is seldom bestowed upon it. 

 Admitting large quantities of cold air into a house, many de- 

 grees below the internal atmosphere, cannot be otherwise than 

 injurious to the plants growing therein. It has been calculated 

 that a volume of air, equal to 400 cubic feet, will absorb up- 

 wards of 36 gallons of water during its rise from 60 to 90° 

 of temperature ; or, in other words, upwards of a gallon has 

 been absorbed for every degree of temperature above 60°. This 

 will, in some measure, show the propriety of keeping the walls 

 and floors of a plant-house continually saturated with moisture, 

 especially during the hot days of summer, as well as of pre- 

 venting currents of air from sweeping through the house. We 

 have succeeded, in this way, in keeping the atmosphere of a 

 green-house 10 or 15° below the external temperature, even 

 when the latter stood above 90° ; and almost every gardener, 

 who has paid attention to these matters, has experienced the 

 same results. It is a common error for gardeners to give large 

 supplies of air, in sultry weather ; but, as it is a practical one, 

 and one of long standing, it is excusable in those who have not 

 studied its effects attentively. 



By far the larger number of gardeners attach great impor- 

 tance to the ventilation of their houses abundantly, without per- 

 haps sufficiently considering the nature of the plants they have 

 to manage ; and, as has been justly enough said, by supposing 

 that plants require to be treated like man himself. They con- 



