SECT. IV. DECOMPOSITE ORGANS* 24Q 



is opened at a small distance from a young tree and 

 immediately filled up again with loose earth, the 

 roots which enter the trench will continue to follow its 

 direction, and will send out but few lateral branches. 

 And if part of the trench is filled up with earth of 

 a superior quality, or with earth mixed with manure, 

 the greater number of divisions will be directed to 

 that quarter. Trees also that are planted by the 

 banks of a river extend their branches chiefly in the 

 directiou of the river without sending out many 

 lateral b ranees ; where the earth is very loose the 

 roots are generally weak, because having no obstacle 

 to overcome they have extended to an undue length. 

 Hence the roots of plants vegetating in pots,, but 

 especially in water, are the weakest ; but where 

 roots have some considerable obstacle to overcome 

 they will often acquire a strength proportioned to 

 the difficulty : sometimes they will penetrate through 

 the hardest soil to get at a soil more nutritive, and 

 sometimes they will insinuate their fibres into the 

 crevices even of walls and rocks which they will 

 burst or overturn. This of course requires much 

 time, and does much injury to the plant. Roots 

 consequently thrive best in a soil that is neither too 

 loose nor too dense ; but as the nourishment which 

 the root absorbs is chiefly taken up by the ex- 

 tremity, so the soil is often more exhausted at some 

 distance from the trunk than immediately around it. 



Du Hamel regards the small fibres of the root Terminal 

 which absorb the moisture of the soil as being compared 



