On the Motions of the Tendrils of Plants. 3A9f 



situations tbev had occupied irj the precedmg mnrning; 

 and they did noi so iinmedialely, or so regularly, bend to- 

 wards the shade of contiguous objects. But as the tendrils 

 of this plant, Hke those oi' the ampelopsis, spr.ng ahemately 

 from eacl) side of the stem, and as one point only in three 

 is without 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 towards the bodv it touches, and, if that body be 

 slender, to attach itself firndy by twining round it, in obe- 

 dience to causes which I shall endeavour to point out. 



The tendril of the vine, in its internal organization, is 

 apparemlv sim.lar to the young succulent shoot, and leaf- 

 stalk, of the same plant ; and it is as abundantly provided 

 with vessels, or passages, for the sap; and j have proved 

 that it is alike capable of feeding a succulent shoot, or a 

 leaf, when grafted upon it. It appears thcrehjre, I con- 

 ceive, not improbable, that a considerable quanlily of the 

 i-novms: fluid of the plant passes through its tendrils; and 

 that there is a close CiUineclion between its vascular struc- 

 ture and its motions. 



I have pioved in the Philosophical Transactions of 1806, 

 that centritugal force, by operating upon the elongating 

 plumules of'germinaling seeds, occasions an increased 

 growth and extension upon the external sides of the young 

 stems, and that iiravitaiion produces correspondent eflTects; 

 probablv by occasioning tlie presence of a larger portion of 

 the fluid organizable matter or 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 tendril, which will consequently con- 

 tract, to the opposite side, which will expand ; and the 

 tendril will thence be compelled to bend round a slender 

 bar of wood or metal, juil as the stems of germinating 

 seeds are made to bend upwards, and to raise the cotyledons 

 out ot the ground; and in support of this conclusion I 

 shall observe, that the sides of tiie tendrils, where in con- 

 tact with the substance they embraced, were compressed 

 and tlatiened. 



The actions of the tendrils of the pea were so perfectly 

 similar to those of the vine, when they came into contact 

 with any body, that I need not trouble you with the obser- 

 vations 1 made upon thai plant. An increased extension of 

 the cellular substance of the bark upon one side of the ten- 

 drils, and a correspondent contraction upon the opposite 



side. 



