DIRECTIOX OF THE GROWTH OF ROOTS. 371 



I shall proceed to state some of the facts, upon which Facts on which 



this opin" 

 founded. 



this hypothesis has been founded ; and others, which have ''"^°'""'''"'* 



occurred in tlie course of my own experience, and which 

 are favourable to it; after which I shall endeavour to 

 trace the elFects observed to the operation of different 

 causes. 



When a tree, which requires much moisture, has sprung Roots tending 

 up, or been planted, in a dry soil, in the vicinity of water, ^"^'^^"^ 

 it has been observed, that much the largest portion of its 

 roots has been directed towards the water; and that when 

 a tree of a different species, and which requires a dry soil, 

 has been placed in a similar situation, it has appeared, in 

 the direction given to its reots, to have avoided the water 

 and moist soil. 



A tree growing upon a wall, at some distance from the Roots from a 

 ground, and consequently ill supplied with food and water, ^"^^^ ^"'^ ^^" 

 lias also been observed to adapt its habits to its situation, 

 and to make very singular and well directed efforts to reach 

 the soil beneath, by means of its roots *. During the period 

 in which it is making such efforts, little addition is made to 

 its branches, and almost the whole powers of the plant ap- 

 pear to be directed to the growth of one or more of its prin- 

 cipal roots. To these much is in consequence annually 

 added, and they proceed perpendicularly towards the earth, 

 unless made to deviate by some opposing body: and as 

 soon as the roots have attached themselves to the soil, the 

 branches grow with vigour and rapidity, and the plant 

 assumes the ordinary habits of its species. 



Du Hamel caused two trenches to be made so as to inter- Tree planted in 

 ject each other at right angles, and a tree to be planted at ^'j^^'^^^^'^'^^^Jie^^ 

 the point of intersection ; and taking up this tree some 

 years afterward, he found that the roots had almost wholly 

 confined themselves to the trenches, in which the soil of the 

 former surface must have been buried. 



A trench, which was twenty feet long, sis wide, and Carrots and 

 about two deep, was prepared in my garden, in the bottom P^^sneps sown 

 of which trench was placed a layer, about six inches deep, with arichsub- 

 Of very rich mould, incorporated with much fresh vegetable ^'^'"^^"'"' 



Smith's Introduction to Botany. 



B b 2 matter. 



