ON THE REPRODUCTION OF BUDS. 123 



biennial plants in common with the turnip or not, I am not at present in 

 possession of facts to decide, not having made precisely the same experi- 

 ment on any other plant. 



I will take this opportunity to correct an inference that I have drawn 

 in a former paper *, which the facts (though quite correctly stated) do 

 not, on subsequent repetition of the experiment, appear to justify. I 

 have stated, that when a perpendicular shoot of the vine was inverted to 

 a depending position, and a portion of its bark between two circular 

 incisions round the stem removed, much more new wood was generated 

 on the lower lip of the wound, become uppermost by the inverted position 

 of the branch, than on the opposite lip, which would not have happened 

 had the branch continued to grow erect, and I have inferred that this 

 effect was produced by sap which had descended by gravitation from the 

 leaves above. But the branch was, as I have there stated, employed as 

 a layer, and the matter which would have accumulated on the opposite 

 lip of the wound had been employed in the formation of roots, a circum- 

 stance which at that time escaped my attention. The effects of gravita- 

 tion on the motion of the descending sap, and consequent growth of 

 plants, are, I am well satisfied, from a great variety of experiments, very 

 great ; but it will be very difficult to discover any method by which the 

 extent of its operation can be accurately ascertained. For the vessels 

 which convey and impel } the true sap, or fluid from which the new 

 wood appears to be generated, pass immediately from the leaf-stalk 

 towards the root ; and though the motion of this fluid may be impeded 

 by gravitation, and it be even again returned into the leaf, no portion of 

 it, unless it had been extravasated, could have descended to the part 

 from which the bark was taken off in the experiment I have described. 

 I am not sensible that in the different papers which I have had the 

 honour to address to you, I have drawn any other inference which 

 the facts, on repetition of the experiments, do not appear capable of 

 supporting. 



* See above, No. III. f See the preceding Papers. 



