I'KRSPinATION. 67 



and the atmosphere is thus kept uniformly 

 moist, not, as in green houses, moist all night 

 and dried by ventilation all day. The only 

 way of growing plants to perfection in rooms, 

 is in these Ward's boxes — and the plants 

 in most glass structures would thrive better 

 with much less ventilation. The greater the 

 heat the more moisture is required. The 

 custom of gardeners seems preposterous, to 

 deluge the floors of green houses with water 

 to create a damp atmosphere, and then ven- 

 tilate freely, which dries it up. This capricious 

 change is very injurious to plants. 



It is thought by some geologists, that the 

 gigantic growth of the plants of former ages, 

 of which such beautiful specimens are daily 

 discovered in coal mines, was favored by the 

 extreme heat and moisture with which the sur- 

 face of the globe was then covered. 



Mr. Knight, in a forcing house devoted to 

 experiment, never gave air to his grapes until 

 nearly ripe, even in hottest and brightest 

 weather, farther than just necessaiy to prevent 

 the leaves being destroyed by excess of heat, 

 and employed very little fire heat. Many hot 

 houses are now built in Europe without any 

 means of ventilation. It must be remembered. 



