20 TWINING PLANTS. Chap. 1 



who found different individuals of Solanum dulcamara 

 twining in opposite directions, and these had their 

 leaves in each case spirally arranged in the same direc- 

 tion. A dense whorl of many leaves would apparently 

 be incommodious for a twining plant, and some authors 

 assert that none have their leaves thus arranged ; but 

 a twining Sijphomeris has whorls of three leaves. 



If a stick which has arrested a revolving shoot, but 

 has not as yet been encircled, be suddenly taken 

 away, the shoot generally springs forward, showing 

 that it was pressing with some force against the stick. 

 After a shoot has wound round a stick, if this be with- 

 drawn, it retains for a time its spiral form ; it then 

 straightens itself, and again commences to revolve. 

 The long, much-inclined shoot of the Geropegia pre- 

 viously alluded to offered some curious peculiarities. 

 The lower and older intemodes, which continued to 

 revolve, were incapable, on repeated trials, of twining 

 round a thin stick ; showing that, although the power 

 of movement was retained, this was not sufficient 

 to enable the plant to twine. I then moved the 

 stick to a greater distance, so that it was struck by 

 a point 2J inches from the extremity of the penulti- 

 mate internode ; and it was then neatly encircled 

 by this part of the penultimate and by the ultimate 

 internode. After leaving the spirally wound shoot for 

 eleven hours, I quietly withdrew the stick, and in the 

 course of the day the curled portion straightened 

 itseK and recommenced revolving ; but the lower and 

 not curled portion of the penultimate internode did 



