lo2 ARTIFICIAL HEAT. 



Heat in the earth occupied by fruit trees has 

 been said by some cultivators to be so important 

 that borders have been prepared, walled, and floored 

 with cement, and pipes have been introduced con- 

 taining it. The trees planted in soil thus prepared 

 have been remarkable for their tine foliage, perfect 

 fruit, and the greater maturity of their wood. This 

 bottom-heat is esteemed highly by all good gar- 

 deners, and its effect on many plants is wonderful. 

 Compare, as an example, two specimens of the same 

 species, — the one growing in an unprepared open 

 soil, and the other plunged in the warm borders of 

 a green-house or hot-bed. 



4. Unpulverized land is sour. Mr. Jos. F. W. 

 Johntson remarks upon this subject : " Under the 

 influence of air, the decomposition of the vegetable 

 matters of the soil proceeds more rapidly ; it is 

 more speedily resolved into those simple forms — 

 carbonic acid and water, chiefly — which are fitted to 

 administer to the growth of new vegetable matter. 

 In the absence of air, not only does decomposition 

 proceed more slowly, but the substances immedi- 

 ately produced by it are frequently unwholesome 

 to the plant, and therefore are fitted to injure or 

 materially retard its growth. 



"When the oxygen of the air is more or less 

 excluded, the vegetable matter of the soil takes this 

 element from such of the earthy substances as it is 

 capable of decomposing, and reduces them to a 



