208 Rev. P. Keith on Phytological Errors, with Admonitions, 



ground I know not, unless as involved in the theory of Mr. 

 Knight, adopts an additional opinion, which I cannot help re- 

 garding as erronepus also. It is the opinion by which vege- 

 tating roots are supposed to receive their increments of length 

 solely by the extreme points. " Les racines ne s'alongent 

 que par leur extremite*." That this was the result of some 

 experiments of Duhamel and of Mr. Knight, we do not mean 

 to deny; but it is good only as far as it goes. You are not to 

 deduce from it a rule for all plants whatever. If you do so, 

 you embrace a manifest error which I did my best to expose, 

 so long ago as 1819, in a set of experiments published in 

 No. 76 of Dr. Thomson's Annals of Philosophy. Yet I 

 do not find that any one ever condescended to notice them, or 

 to embrace the truth which they establish on account of them. 

 Truth, lovely though she be, if she hopes to be well received, 

 must come with a recommendation in her right hand, that is, 

 a recommendation from some great and acknowledged autho- 

 rity ; for there are many sciolists who would rather be in the 

 wrong with a writer of high reputation than in the right with 

 one of minor celebrity. Yet I find that Mr. Lindley has at 

 last taken up the subject, and exposed the erroneousness of 

 the old opinion f, so that from henceforward it is to be be- 

 lieved that botanists will no longer be found to cling to this 

 palpable error. " On the 5th of August," says Mr. Lindley, 

 " I tied threads tightly round the root of a Vanilla, so that it 

 was divided into three spaces, of which one was 7 inches long, 

 another 4 inches, and a third, which was the free growing 

 extremity, 1 inch and fths. On the 19th of September the 

 first space measured 7J inches, the second 4f inches, and 

 the third, or growing, 2£ inches." A root of Aerides cor- 

 nutum gave a similar result, and established the fact of the 

 general elongation of the root in the plants specified. Yet 

 Mr. Lindley gives all the weight that is due, or perhaps even 

 more than is due, to the experiments of Duhamel and Mr. 

 Knight; for he thinks it is possible that the peculiarity of 

 elongation by the extreme points may be universal in exoge- 

 genous plants. But the experiments which I instituted on the 

 radicle of the bean show that it is not. 



"On the first of October 1818, I sowed some tick beans 

 in a small earthen pan filled with garden mould. 



" On the fourth the radicle of the most forward had pro- 

 truded about -i-th of an inch beyond the integuments, when I 

 marked it with ink at the point, in the middle, and at the base, 

 as clearing the integuments ; so that the marks were about 

 -j^th of an inch from each other. 



* Phys. Vegct., torn. i. p. 41 ; ii. p. 822. 1 tntrod., p. 228. 



