LEAr-CLTMBERS. 41 



some little force. The petioles, when coming into contact with a 

 stick, take either a complete or half turn round it ; ultimately they 

 increase much in thickness. Leaves arising on the side of the 

 stem opposite to the ffght move towards it ; and, in doing so, the 

 petioles are sometimes brought into contact with the stem, and 

 consequently clasp it ; but the petioles have no true spontaneous 

 movement". 



Lophospermum scandens, var. purpureum, — Some long, mode- 

 rately thin intemodes made four revolutions at an average rate of 

 3 h. 15 m. The course pursued was very irregular — sometimes an 

 extremely narrow ellipse, sometimes a large circle, sometimes an 

 irregular spire or zigzag line, and sometimes the apex stood still. 

 The young petioles, when brought by the revolving movement into 

 contact with a stick, clasp it, and soon increase considerably in 

 thickness ; but they are not quite so sensitive to a light weight 

 as those of the HJiodoeJiiton, for loops of thread weighing one- 

 eighth of a grain did not invariably cause them to bend. 



This plant presents a case not observed in any other leaf- 

 climber or twiner or tendril-bearer, or in any other plant as far as 

 I know, namely, that the young internodes are sensitive to a 

 touch- "Wlien a petiole clasps a stick, it draws the base of the 

 intemode against it ; and then the internode itself bends towards 

 the stick, which is thus caught between the stem and the petiole 

 as by a pair of pincers. The internode straightens itself again, 

 excepting the part in contact with the stick. Young internodes 

 alone are sensitive, and these are sensitive on all sides along their 

 whole length. I made fifteen trials by lightly rubbing two or 

 three times Avith a thin twig several intemodes ; and in about 2 h., 

 but in one case in 3 h,, all became bent ; they became straight again 

 in about 4 h., subsequently. An intemode, which was rubbed as 

 much as six or seven times with a twig, became just perceptibly 

 curved in 1 h. 15 m., and subsequently in 3 h. the curvature in- 

 creased much ; the internode became straight again in the course 

 of the night. I rubbed some internodes one day on one side, and 

 the next day on the opposite side or at right angles ; and the cur- 

 vature was always towards the rubbed side. 



According to Palm (S. 63), the petioles oi Linaria cirrhosa and, 

 to a limited degree, those of L, elatine have the power of clasping 



a support. 



SoLA^UM. — S. Jasminoides. — Some of the species of this large 

 genus are twiners ; but this is a true leaf-climber. A long, nearly 

 upright shoot made four revolutions, moving against the sun, very 



