72 



ME. DAUWIN ON CLIMBIKG TLA^'TS. 



( 



weighing only the one-sixteeuth of a grain caused them, in under 

 4h., to become greatly curved : when the loop was removed, the 

 petioles straightened themselves in about the same time. The 

 petiole (e) was rather less sensitive ; and in another specimen, in 

 which the corresponding petiole bore rather larger leaflets, a loop 

 of thread weighing one-eighth of a grain did not cause curvature 

 until 18 h. had elapsed. Loops of thread weighing one-fourth of a 

 grain, left suspended on all the lower petioles (/to T) during several 

 days, produced no effect; Tet the three petioles/ g, and h are not 

 quite insensible, for when left in contact with a stick for a day or 

 two they slowly curled round it. So that the sensibility of the 

 petiole gradually diminishes from the tendril-like extremities to 

 the base. The internodes are not at all sensitive, which makes 

 Mohl's statement that they are sometimes converted into tendrils 

 the more surprising, not to say improbable. 



The whole leaf, whilst young and sensitive, stands almost ver- 

 tically upwards, as we have seen is the case with many tendrils. 

 It is in continual movement, and one that I observed swept 

 large, though irregular, ellipses, sometimes narrow, sometimes 

 broad, with their longer axes directed to different points of the 

 compass, at an average rate of about 2h. for each revolution. The 

 young internodes also, which bear the revolving leaves, likewise 

 revolve irregularly in ellipses and spires ; so that by these com- 

 bined movements a considerable space is swept for a support. If 

 the terminal and attenuated portion of the petiole fails in seizing 

 any object, it ultimately bends downwards and inwards, and then 

 soon loses all its irritability and power of movement. This bend- 



ery 



ounpt leaves in many SDecies of Clematis 



of sensitiveness. 



fuU 



Uctrifolia. — In this allied plant 



of the terminal leaflets has heen complete, and they are converted 

 into perfect tendrils. Whilst the plant was young, the ten- 

 drils appeared like modified branches, so that a distinguished 



nature 



Hooker 



tendrils are modified leaves. The tendrils, when of full size, are 

 above 5 inches in lengtli ; they bifurcate twice, thrice, or even 



t)ranches of the tendrils are sensitive on all 



blunt. AU the 



