TENDRILS OF PLANTS: 41 



and they did not subsequently shew any disposition to approach 

 the points from which they once receded. The tendrils of 

 the vine, on the contrary, varied their positions in every period 

 of the day, and after returned again during the night, to the 

 situations they had occupied in the preceding morning j and 

 they did not so immediately, or so regularly, bend towards 

 the shade of contiguous objects. But as the tendrils of this 

 plant, like those of the ampelopsis, spring alternately from 

 each side of the stem, and as one point only in three is with- 

 out a tendril, and as each tendril separates into two divisions, 

 they do not often fail to come into contact with any object 

 within their reach ; and the effects of contact upon the tendril 

 are almost immediately visible. It is made to bend towaids 

 the body it touches, and if that body be slender, to attach 

 itself firmly, by twining round it, in obedience to causes which 

 I shall endeavour to point out. 



The tendril of the vine, in its internal organization, is ap- Explanation of 

 parently similar to the young succulent shoot, and leaf-stalk, J^ ^^rTdrilT <5 

 of the same plant j and it is as abundantly provided with ves- the vine as- 

 sels or passages for the sap j and I have proved, that it Is SSTaiSf cur- 

 alike capable of feeding a succulent shoot, or a leaf, when vature. 

 grafted upon it. It appears, therefore, I conceive, not impro- 

 bable, that a considerable quantity of the moving fluid of the 

 plant passes through its tendrils j and that there is a close con- 

 nection between its vascular structure and its motions. 



I have proved, in the Philosophical Transactions of 180(5, 

 that centrifugal force, by operating upon the elongating plu- 

 mules of germinating seeds, occasions an increased growth 

 and extension upon the external sides of the young stems, and 

 that gravitation produces correspondent effects j probably by 

 occasioning the presence of a larger portion of the fluid orga- 

 nizable matter of the plant upon the one side, than upon the 

 other. The external pressure of any body upon one side of a 

 tendril, will probably drive this fluid from one side of the ten- 

 dril, which will consequently contract to the opposite side, 

 which will expand $ and the tendril will thence be compelled 

 to bend round a slender bar of wood or metal, just as the 

 stems of germinating seeds are made to bend upwards, and to 

 raise the cotyledons out of the ground j and in support of this 

 conclusion I shall observe, that the sides of the tendrils where 



in 



