LEAF-CLIMBEKS. 



25 



Dublin twined up sticks above 8 feet in height. These facts 

 are highly remarkable ; for there can hardly be a doubt that in 

 the dryer provinces of South Africa these plants must have propa- 

 gated themselves for thousands of generations in an erect condi- 

 tion ; and yet during this whole period they have retained the 

 innate power of spontaneously revolving and twining, whenever 

 their shoots become elongated under proper conditions of life. 

 Most of the species of Phascolus are twiners ; but certain varieties 

 of the P. multijlorus produce (Leon, p. 681) two kinds of shoots, 

 some upright and thick, and others thin and twining. I have 

 seen striking instances of this curious case of variability with 

 "Fulmer's dwarf forcing-bean," on which occasionally a long 

 twining shoot appeared. 



Solanum dulcamara is one of the feeblest and poorest of twiners : 

 it may often be seen growing as an upright bush, and when 

 growing in the midst of a thicket merely scrambles up the 

 branches without twining ; but when, according to Dutrochet 

 (torn. xix. p. 299), it grows near a thin and flexible support, such 

 as the stem of a nettle, it twines round it. I placed sticks round 

 several plants and vertical stretched strings close to others, and 

 the strings alone were ascended by twining. "We here, perhaps, 

 sec the first stage in the habit of twining; and the stem twines 

 indifferently to the right or the left. Some other species of the 

 genus, and of another genus, viz. Habrotliamnus, of the same family 

 of Solanacese, which are described in horticultural works as twining 

 plants, seemed to possess this faculty in a very feeble manner. 

 On the other hand, I suspect that with Tecoma radicans we have 

 the last vestige of a lost habit: this plant belongs to a group 

 abounding with twining and with tendril-bearing species, but it 

 ascends by rootlets like those of the Ivy ; yet I observed that the 

 young internodes seldom remained quite stationary, but performed 

 slight irregular movements which could hardly be accounted for 

 by changes in the action of the light. Anyhow it need not be 

 supposed that there would be any difficulty in the passage from a 

 spirally twining plant to a simple root-climber; for the young 

 internodes of Bignonia Tieecdyana and of Hoya car?iosa revolve 

 and twine, and likewise emit rootlets which adhere to any fitting 

 surface. 



Part II. — Leaf-cltmbebs. 

 It has long been observed that several plants climb by the aid of 

 their leaves, either by the petiole or by the produced midrib; 

 but beyond this simple fact nothing is known of them. Palm 



