52 MB. DARWIN ON CLIMBING PLANTS. 



in comparison with those of the previous species. The lower 

 part, or tarsus, is four times as long as the three toes ; these 

 are of equal length ; they do not lie in the same plane, but diverge 

 equally on all sides ; their tips are bluntly hooked, so that the 

 whole tendril makes an excellent grapnel. The tarsus is sensitive 

 on all sides ; but the three toes are sensitive only on their outer 

 surfaces, which correspond with the under surfaces of the toes in the 

 tendrils of the previous species. The sensitiveness is not much 

 developed ; for a slight rubbing with a twig did not cause the tar- 

 sus or toes to become slightly curved until an hour had elapsed ; 

 subsequently they straightened themselves. Both tarsus and toes 

 can seize well hold of sticks. "When the stem is seciu-ed, the ten- 

 drils are seen spontaneously to sweep large ellipses : the two 

 opposite tendrils move independently of each other. I have no 

 doubt, from the analogy of the two following allied species, that 

 the petioles move spontaneously ; but they are not irritable like 

 those of B. ungtiis and B. Twee.dyana. The young internodes 

 also sweep fine large circles, one being completed in 2h. 15 m., 

 and a second in 2 h. 55 m. By these combined movements of the 

 internodes, petioles, and grapnel-hke tendrils, the latter are soon 

 brought into contact mth surrounding objects. When a shoot 

 stands near an upright stick, it twines regularly and spirally round 

 it ; as it ascends, it seizes the stick with only one of its tendrils, 

 and, if the stick be thin, the right- and left-hand tendrils 

 are alternately used. This alternation follows from the stem 

 necessarily taking one twist round its own axis for each com- 

 pleted spire. 



The tendrils a short time after catching any object contract 

 spirally. Those which have caught nothing slowly bend down- 

 Avards, but do not contract spirally. AA^ith many plants the 

 tendrils after a time contract spirally, whether or not they have 

 caught any object. But this whole subject of the spiral contrac- 

 tion of tendrils will be discussed after the several tendril-bearing 

 plants have been described. 



Bigmnia littoralk .—"^^ young internodes revolve in fine large 

 ellipses. An internodc bearing immature tendrils made tAVO revo- 



performed 



grown 



But tliis species, unlike the preceding, is incapable of spiraU/ 

 twining round any object : this did not annear due to any want 



intemode 



and certainly not to any want of the revolving power ; nor can I 



