The Story-Book of the Fields 



method of improvement is very slow and takes 

 several years. It may be shortened by 

 ploughing, or even by supplying manure, 

 although it is not to be sown immediately. 



But there is a way of getting crops from the 

 same land uninterruptedly, unless it is very 

 poor. All plants are nourished at the expense 

 of the earth and the air, but some take most 

 from the former and others from the latter. 

 The plants which draw most of their food from 

 the air are those with highly developed foliage, 

 such as the potato. We know that it is by 

 means of their leaves that plants absorb the 

 carbonic gas dispersed in the air, so that the 

 larger and more numerous the leaves the 

 more abundant will be the absorption. The 

 plants that take almost everything from the 

 ground are those the leaves of which are few, 

 small and thin, and which can therefore 

 absorb but little carbonic acid gas from the 

 air. Such an one is wheat. 



On the other hand, nothing of the potato is 

 used except the tubers, which are only a small 

 part of the whole plant, while the stalk and 

 the foliage are buried in the ground and con- 

 verted into humus. So the potato enriches 

 the ground with the substances that it has 

 absorbed from the air ; and gives more than 



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