406 



NOTES AND ILLUSTRATIONS. 



Agriculture entirely agrees in the sentiment expressed in the text, 

 regarding the renovation of the tap-roots in trees. 



" The opinion,'' he observes, " that young plants have not the power 

 of renewing their tap-roots, will, we believe, be found inconsistent with 

 fact ; and we may appeal to Sang, and other nurserymen, who raise 

 the Oak and Horse-Chestnut from the seed. It is customary, when 

 these are sown in drills, to cut off their tap-roots, without removing 

 the plants, at the end of the second year's growth ; and when, at the 

 end of the third and fourth year, they are taken up, they will be found 

 to have acquired other tap-roots — not indeed so strong as the first would 

 have been, had they remained, but sufficient to establish the fact of the 

 Ijower of renewal. We may also refer to the experiments recorded by 

 Forsyth, which at once prove that trees have the power of renewing 

 their tap-roots, and the great advantages resulting from cutting down 

 trees after two or three years' planting. Forsyth says, * that he trans- 

 planted a bed of Oak plants, cutting the tap-roots near to some of the 

 side-roots, or fibres springing from them. In the second year after, he 

 headed one half of the plants down, and left the other half to nature. 

 In the first season those headed down made shoots six feet long, and 

 upwards, and completely covered the head of the old stem, leaving only 

 a faint cicatrix, and produced new tap-roots upwards of two feet and a 

 half long.' "— Encyclop. of Agricul. Part III. Book ii. p. 572. 



The power, which tap-roots unquestionably possess, of renewal after 

 being cut, is a point of considerable interest to the art under discussion : 

 and it is important that it should be ascertained beyond controversy^ 

 that the cutting of them under ground does no material injury to trees ; 

 otherwise it would follow that all removal is materially injurious. 



Before we quit the subject of tap-roots, it is worthy of notice, that 

 the ingenious Mr Knight, to whom phytological science is under so 

 many obligations, has suggested the notion that gravitation is the agent 

 employed by nature to make the germens of plants ascend in the air, 

 and their radicles go down into the earth ; and this doctrine he has 

 endeavoured to establish on the ground of experiment. See Philos. 

 Trans. 1806, pp. 100, 101, et seq. But it seems much more reasonable 

 to believe, that the radicles of trees possess energies quite capable of 

 counteracting the influence of gravitation, when needful, and that it 

 does not constitute the sole, or even the principal agent of nature in this 

 business. If gravitation were the sole cause of giving a direction to 

 roots, it might be asked why roots select the best soil in descending, 

 which they are well known to do ? Because, if acted on only by gravita- 

 tion, they would have no choice but to descend, unless prevented by 

 some obstacle that could not be surmounted. Such an obstacle might 



