176 TENDRIL-BEAKERS. Chap. IV. 



the part which is wound round a support which 

 chiefly becomes thicker and stronger; I have seen, 

 for instance, this part of a tendril of Bignonia scqui- 

 noctialis twice as thick and rigid as the free basal part. 

 Tendrils which have caught nothing soon shrink and 

 wither ; but in some species of Bignonia they disarti- 

 culate and fall off like leaves in autumn. 



Any one who had not closely observed tendrils of 

 many kinds would probably infer that their action was 

 uniform. This is the case with the simpler kinds, 

 which simply curl round an object of moderate thick- 

 ness, whatever its nature may be.* But the genus 

 Bignonia shows us what diversity of action there may 

 be between the tendrils of closely allied species. In 

 all the nine species observed by me, the young in- 

 ternodes revolve vigorously; the tendrils also re- 

 volve, but in some of the species in a very feeble 

 manner ; and lastly the petioles of nearly all revolve 

 though with unequal power. The petioles of three of the 

 species, and the tendrils of all are sensitive to contact. 

 In the first-described species, the tendrils res mble 

 in shape a bird's foot, and they are of no service to the 

 stem in spirally ascending a thin upright stick, but 

 they can seize firm hold of a twig or branch. When 



* Sachs, however (' Text-Book adapted to clasp supports o{ 



of Botany,' Eng. Translation, ]S75, different thicknesses. He further 



p. 280), has shown that which shows that after a tendril has 



I overlooked, namely, that the clasped a support it subsequently 



tendrils of different species are tightens its hold. 



