Jafl.'] THE FORCING GARDEN. 557 



with that highly useful and delicate salad in a state so good, 

 as that where it is cultivated in the usual manner ? Although 

 pines will grow without bottom heat, still we have the experi- 

 ence of many years, and also of many intelligent cultivators, 

 that they will grow in bottom heat much better ; and although 

 the heat of the soil in which the pine grows in its native coun- 

 try may never exceed, and seldom equals that of the surround- 

 ing atmosphere, yet it does not follow that earth heated to a 

 gi-eater degree may not be of service to it, in an artificial state 

 of cultivation. Our indigenous plants, Cromhe ISIarithna, 

 sea-kale ; and some others, are brought to the greatest 

 perfection, by being cultivated in a temperature much higher, 

 in proportion to their natures, than has ever been attempted 

 with the pine. The conclusions drawn by an intelligent 

 writer upon this subject are in exact correspondence with 

 our own. "It appears from nature," says he, " as well 

 as from observing v/hat takes place in culture, that the want 

 of a steady temperature and degree of moisture at the 

 roots of plants, is more immediately and powerfully inju- 

 rious to them than atmospheric changes. Earth especially, if 

 rendered porous and sponge-like by culture, receives and gives 

 out air and heat slowly ; and while the temperature of the air 

 of a country, or a hot-house, may vary twenty or thirty de- 

 grees in the course of twenty-four hours, the soil at the depth 

 of two inches would hardly be found to have varied one de- 

 gree. With respect to moisture, every cultivator knows that 

 in a properly constituted and regularly pulverized soil, what- 

 ever quantity of rain may fall on the surface, the soil is never 

 saturated with water, nor in times of great drought burnt up 

 with heat. 1 he porous texture of the soil and sub-soil being 

 ,at once favorable for the escape of superfluous water, and ad- 

 verse to its evaporation, by never becoming so much heated 

 on the surface, or conducting the heat so far downwards as a 

 close compact soil. These properties of the soil, relative to 

 plants, can never be completely attained by growing plants in 

 pots, and least of all by growing in pots surrounded with air. 

 In this state, whatever n:ay be the care of the gardener, a 

 continual succession of changes of temperature will take place 

 in the outside of the pot, and the compact material of which U 



