SOILS AND CLIMATES SUITABLE. 29 



would absorb from the atmosphere the necessary supplies. 

 This probably is the condition under which it thrives in 

 its native home. On the Pacific coast of America rain 

 is of rare occurrence, consequently the surface soil is com- 

 paratively dry, and can furnish but scanty supplies to 

 the thirsty vegetation of an intertropical country. But 

 although the rainfall of other climates is unknown there, 

 the air is charged with moisture, which, when the tem- 

 perature falls towards sunset, is set free, and deposited on 

 the leaves in the shape of dew, the absorbent powers of 

 the leaves enabling them to drink in the vital fluid suffi- 

 cient to supply their own natural processes, and to replace 

 that which they had given out under the influence of the 

 solar rays. On peat and bog lands, good crops are fre- 

 quently obtained. The previous application of lime to 

 such soils is always followed by beneficial results; the 

 inert, or sometimes noxious matters combine chemically 

 with the lime, and are neutralized or converted into valu- 

 able compounds, while, at the same time, it produces a 

 mechanical effect on the mass, by giving it a greater soli- 

 dity, and increasing its powers of absorption and retention 

 of moisture. On soils of this description, where the straw 

 crops are often limited to oats, potatoes generally enter 

 into the system of farming, and form a very profitable 

 crop to alternate with turnips in the rotation. In all 

 cases, no matter what the character of the soil may be, it 

 is important that it be free from stagnant water, and that 

 the tillage processes be such as to secure a good depth 

 and a fine division of the soil, so that the air may have 

 good access to it, and exert its full oxidizing influence 

 on the various ingredients. 



If we look at the arrangement of the potato plant in its 

 growing state, we see at once how far the physical condi- 

 tions of the soil are likely to affect it. We have the 

 erect stem and leaves appearing above the surface, and 



