142 Food from the Soil 



be found to be pretty nearly the same ; the proportion 

 will be the same, that is to say, for of course, in un- 

 favourable soil, the plant may be a dwarf. Grasses, 

 for instance, which are like corn in taking in consider- 

 able quantities of silica, will take up just as much of 

 this when they grow on the chalk soil of the downs as 

 when they grow in a soil containing much sand. Yet 

 chalk, pure chalk, does not contain a particle of silica. 



As before remarked, however, such a thing as a 

 perfectly unmixed soil is hardly to be found anywhere. 

 Even on the mountains there is rarely less than ten 

 per cent, of soil which has been brought from 'else- 

 where, either by wind or water, or added to it by 

 animals. So it is on the downs, and the grass finds 

 there what it needs. 



It would be rash to say of any plant that it will not 

 grow on any soil until it has been tried; but plants 

 certainly have their likes and dislikes in this matter, 

 though sometimes a good climate will make up for 

 poor soil. 



Clover, for instance, loves lime; and cowslips and 

 primroses are poor and scanty where lime is deficient, 

 and luxuriant on chalk; but the heather, in this country 

 at all events, shuns lime ; and though it may be found 

 growing close by on a patch of sand, and though its 

 seeds must be scattered all around, it is not to be found 

 on the chalk downs. Here and there a stray plant 

 may be seen growing in a mixture of sand and chalk ; 

 but as a rule it is conspicuously absent from chalk 

 and limestone in England, and in Wurtemberg it 

 actually disappears even from sandy soils, if marl 

 containing more than a fifth part of lime be added to 

 them. But the same thing does not hold good in 



