82 UPWARD GROWTH OF THE HEAD, AND pt. ii. 



root is found to grow liorizoiitally, or sloping upward 

 or downward, according to the inclination of the 

 ground. I consider the idea of the tap-root of the oak 

 (except as a seedling) to be a vulgar error. I have 

 never seen any trace of a root at any great distance from 

 the surface of the ground ; nor do the stumps of oaks, 

 when grubbed, show any symptom of a tap-root more 

 than other trees. But the question of the existence of 

 tap-roots in large oaks or other timber- trees should not 

 be argued as a matter of opinion, but proved as a mat- 

 ter of fact. The negative, indeed, cannot be proved. 

 I could produce any required number of oaks with- 

 out the tap-root, but this would not prove that others 

 were without it. Let those who assert the affirmative 

 produce one instance. 



The celebrated Duhamel, wishing to protect his 

 field from robbery from the roots of a row of elms, cut 

 a deep ditch between the elms and his field. The 

 roots, however were not to be done. They of course 

 followed the surface of the ground, whether down, 

 horizontal, or up hill, and took the ditch ' in and out 

 clever ' into the philosopher's field. Duhamel thinks 

 these were very cunning roots, and that they had an 

 instinctive notion of the treat they were to have on the 

 other side of the ditch, ard grew at it. Had the 

 philosopher built a wall in the ditch, and then filled it 

 in, he would have beaten the roots, on account of their 

 inability to leave the surface and get under the wall. 

 Turges- Were we to add one step to the beautiful theories 



cence, and 



