S6 



THE PRACTICAL GARDENER. 



and thus, by multiplying the number of organs, the plants wili 

 of course collect a greater quantity of food. 



The capillary attraction, or that property, which renders the 

 humidity of the soil more uniform, is also promoted by trench- 

 ing, digging, &c. It is evident, that those soils must be the 

 ch'iest, where the particles of the soil are either naturally of 

 the finest kind, such as sand, or rendered fine by digging or 

 trenching. We find that gravels and sands, which are natur- 

 ally reduced to fine particles, hardly retain any water at all, 

 and frequently not even suflScient for the growth of vegetables, 

 which is the cause of their sterihty ; whereas, on the other 

 hand, clays not acted on by artificial operations, either do not 

 absorb water, or when they do, they retain too much. Water 

 is not only necessary to the growth of plants, but also to the 

 production of extract fi'om the vegetable matter which they 

 contain, and unless the soil be brought to that condition, so as 

 to retain a certain quantity of water, just sufficient and no more 

 to produce this extract, all endeavours to fertilize, by means of 

 manures, will be fruitless. 



Manure is of no use to vegetation until it becomes soluble 

 in water, and it would remain in that useless condition if it 

 abounded so as to exclude the air, for v/ithout air, the fibres, 

 or mouths of plants, would be unable to perform their functions, 

 and so decay, and rot oft*. This principle, we see completely 

 exemplified in the roots of plants in pots, when over watered, 

 which gradually decay, and the plant dies. 



To admit the beneficial effects of air, as much as possible, 

 is an important object. Dr. Darwin mentions, " the great pro- 

 priety of cropping lands immediately after they have been com- 

 " oinuted or turned over ; and this the more especially, if ma- 

 nure has been added at the same time, as the process of fer- 

 mentation will go on faster when the soil is loose, and the 

 interstices filled with air, than afterwards, when it becomes 

 compressed by its own gravity, the relaxing influence of rains, 

 and the repletion of the partial vacuums formed by the decom- 

 j>osition of the enclosed air. The advantage of the heat thus 

 obtained, in exciting fermentation, whether in a seed or root, 

 especially in the spring, when the soil is cold, must be con- 

 siderable." 



