132 Roofs 



into the fortieth part of a cubic foot of soil, a quantity 

 which would be contained in a box between three and 

 four inches square and equally deep. 



Of course, if these roots had had their liberty they 

 would have been much less branched, and would have 

 spread much further. They would, so to say, have 

 gone much further ahead, without running up so many 

 by-paths. But being prisoners, they had to make 

 the most of what they had, and so explored most 

 thoroughly the small space at their command. Every- 

 one knows what a mat of roots and fibres there will be 

 when a plant is taken out of a pot too small for it; such 

 a mat that the earth is often completely enveloped. 



Now, of course, it is not natural for a plant to grow 

 in a confined space, with its roots crowded together in 

 this way, and when left to grow as it likes, in the open 

 ground, its roots often roam to great distances, and 

 therefore require much more soil than they make use 

 of as food. The poorer the soil the farther the roots 

 spread in their endeavour to find nourishment, and a 

 maize-plant in sandy soil will send its roots out a dis- 

 tance of ten or fifteen feet. 



It is supposed that only a very small portion, perhaps 

 a hundredth part, of the soil helps to feed the plants 

 growing in it. And this is probable enough when we 

 consider it ; for the soil, however fine, still consists of 

 solid particles, which the roots cannot swallow ; and 

 though it is being constantly dissolved by water and 

 gases, the process is a slow one. Where the soil is 

 coarse the process is slower still. For, as a lump of 

 sugar takes much longer to dissolve than the same 

 quantity of sugar when reduced to powder, just so it 

 is with the soil ; when it is fine the water has a very 



