Chap. IV. SUMMARY. 177 



the stem twines round a somewhat thick stick, a slight 

 degree of sensitiveness possessed by the petioles is 

 brought into play, and the whole leaf together with 

 the tendril winds round it. In B. unguis the petioles 

 are more sensitive, and have greater power of raove- 

 ment than those of the last species ; they are able, 

 together with the tendrils, to wind inextricably round 

 a thin upright stick; but the stem does not twine 

 so well. B. Tweedyana has similar powers, but in 

 addition, emits aerial roots which adhere to the wood. 

 In B. venusta the tendrils are converted into elongated 

 three-pronged grapnels, which move spontaneously in 

 a conspicuous manner ; the petioles, however, have lost 

 their sensitiveness. The stem of this species can twine 

 round an upright stick, and is aided in its ascent by 

 the tendrils seizing the stick alternately some way 

 above and then contracting spirally. In B. littoralis 

 the tendrils, petioles, and internodes, all revolve spon- 

 taneously The stem, however, cannot twine, but ascends 

 an upright stick by seizing it above with both tendrils 

 together, which then contract into a spire. The tips 

 of these tendrils become developed into adhesive discs. 

 B. speciosa possesses similar powers of movement as 

 the last species, but it cannot twine round a stick, 

 though it can ascend by clasping the stick horizon- 

 tally with one or both of its unbranched tendrils. 

 These tendrils continually insert their pointed ends 

 into minute crevices or holes, but as they are always 

 withdrawn by the subsequent spiral contraction, the 

 habit seems to us in our ignorance useless. Lastly, 



