OP BOTTOM HEAT 107 



the soil, at 6 inclies below the surface, was 61° ; at 

 9 inches, 57° ; at 18 inches, 50° ; and at 3 feet, 44°. 

 He took measures to confine the roots to the soil near 

 the surface, and the consequence was, the disappear- 

 ance of canker, and ripening of the fruit. {Memoirs 

 of Cahdonian Sort. Soc. vi. part 2 ; and Gardener''s 

 Magazine, vii. 55.)* 



If, on the other hand, we take cases of growth in 

 the artificial climate of hot-houses, we find that Bigno- 

 nia venusta, and many other tropical plants, will not 



* This must be understood by our readers as applicable to the 

 climate of England. In that temperate and damp climate, the great 

 drawback to the cultivation is the coldness of the soil. In this 

 country, where there is five times more sunshine and heat than in 

 Great Britain, the drawback is of the opposite kind, viz. the dry- 

 ness and want of moisture in the soil during a good part of the sum- 

 mer. Instead, therefore, of its being desirable to confine the roots 

 near the sui-faoe, we find it of the greatest advantage in almost any 

 species of culture, and especially for fruit-trees, to deepen the soil 

 by trenching or sub-soil ploughing, so that the roots can run 

 down twice the usual depth. This not only gives them a larger 

 area from which to obtain their food, but, by placing the food 

 deeper, it maintains that moisture and temperature which enable 

 the roots to go on supplying the demands of the leaves, and keeping 

 up growth, when trees in shallow soil cease growing, and 

 become parched and starved by the heats of midsummer. We 

 may add that canker, or a diseased state of the sap, usually arises in 

 this country, not from coldness of the soil, but from sudden alterna- 

 tions of temperature. The blights of the pear, apricot, and other 

 trees, the most fatal diseases in the United States, are forms of 

 canker induced by sudden thawing of the sap vessels after severe 

 frost. Except in New England and the extreme northern portions 

 of the country, a northern exposure is found preferable to a southern 

 one for orchards and fruit gardens, on account of the greater uni- 

 formity of temperature, and the much lessened tendency to disease 

 in the trees so situated. A. J. D 



