54 MR. DARWIN ON CI.IMIilXli PLANTS. 



Not only the tendrils, but the petioles bearing them, revolve; 

 these petioles, however, are not in the least sensitive. Thus the 

 young internodes, the petioles, and the tendrils, all at the same 

 lime, go on revolving together, but at different rates. Moreover, 

 the movements of the opposite petioles and tendrils are quit© 

 independent of each other. Hence, when the whole shoot is 

 allowed freely to revolve, nothing can be more intricate than 

 the course and rate followed by the extremity of each tendril. A 

 wide hemisphere above the shoot is irregularly searched for some 

 object to be grasped. 



One other curious point remains to be mentioned. Some few 

 days after the toes have closely clasped a stick, their blunt extre- 

 mities become, though not invariably, developed into irregular 

 disk-like balls, which have the singular power of adhering firmly 

 to the wood. As similar cellular outgrowths will be fully de- 

 scribed under B. caprcolata, I will here say nothing more about 

 them. 



Bignoiiia (cquinoctialis, var. Chamherlaijnii. — The internodes, 

 the elongated non-sensitive petioles, and the tendrils all have the 

 power of revolving. The stem does not twine, but ascends a ver- 

 tical stick in the same manner as the last species. The tendrils 

 resemble those of the last species, but are shorter; the three 

 toes are more unequal in length, two of them being about one- 

 third shorter, and rather thinner than the third ; but they vary 

 in these respects. They terminate in small hard points ; and 

 what is important, they do not develope cellular adhesive disks. 

 The reduced size of two of the toes, and their lessened sensitive- 

 ness, seem to indicate a tendency to their abortion ; and the first- 

 formed tendrils on one of my plants were sometimes quite simple. 

 We are thus naturally led to the three following species with 

 simple undivided tendrils. 



Bignonia speciosa. — The young shoots revolve irregularly, 

 making narrow ellipses, or spires or circles, at rates varying from 

 3 h. 30 m. to 4 h. 40 m. ; but the plant shows no tendency to twine. 

 Whilst very young and not requiring any support it does not 

 produce tendrils. The tendrils of a rather young plant were five 

 inches in length; they revolve spontaneously, as do the short 

 and not sensitive petioles. The tendrils, when rubbed, slowly 

 bend to the rubbed side, and subsequently straighten themselves; 

 but they are not highly sensitive. There is something strange in 

 their action : I repeatedly placed upright, thick and thin, rough 

 and smooth sticks and posts, and string suspended vertically, near 



