568 Cultivation of Plants. 



The rainfall varies throughout these countries proportionate 

 to their extent in the same ratio as in the British Islands, and 

 according to local influences ; but as we have records for a few 

 localities only, we forbear giving them. 



One more observation should be made respecting the fore- 

 going figures that they must be treated as rough approxima- 

 tions, both those relating to temperature and to latitude. And 

 we may here repeat, that the cultivator's special study should 

 be the soil and climatal conditions of his own locality. 



3. SOILS, THEIR NATURE AND COMPOSITION. 



So much depends upon the nature of the soil affected by 

 different plants, that we should like to devote much more 

 space than we have at our disposal to the consideration of this 

 question. Under the most favourable climatal conditions 

 many plants have no chance of flourishing unless they are sup- 

 plied with, or placed in, a suitable soil. It is true that a vast 

 majority of plants will succeed in any ordinary, free, tolerably 

 rich soil ; but, on the other hand, there are others that prefer a 

 light dry soil, a rich heavy moist soil, or a peaty soil, and so on. 



According to the composition of the soils, the greater or less 

 will be their power of absorbing and radiating heat, and re- 

 taining or discharging moisture. In other words, a soil may 

 be either a good or bad conductor of heat ; and evaporation 

 and downward drainage of water will be either slow or rapid, 

 in proportion to its density and depth. It is obvious, there- 

 fore, that the extremes of these conditions though both are 

 suitable for certain classes of vegetation are alike uncongenial 

 to the majority of ornamental plants in cultivation. From 

 observations in Scotland, 1 over a period of nine years, the 

 temperature at three inches below the surface has fallen to 

 26-5 in loose sandy soils, and at a depth of twelve inches the 

 freezing point has only once been registered. In clayey soils, 

 on the other Ijand, the lowest temperature at three inches was 

 28, whilst at twelve inches it frequently fell to the freezing 

 point, and once even 32 was recorded at a depth of twenty-two 

 inches. Hence it follows that a moderately light porous, 

 sandy soil, being a feeble conductor of heat, and readily part- 

 ing with its moisture by evaporation and drainage, is emi- 

 nently adapted for tender shrubs, bulbous plants, &c. A heavy 



1 Buchan, ' Handbook of Meteorology.' 



