112 Ml?. DARWIN ON CLIMBING PLANTS. 



species of the Antirrhinece, of Solanwn, of Cocculics, of Gloriosa 

 are related to other genera in the same family, or even to other 

 species in the same genus, which are true twiners. On the 

 other hand, the leaf-climbing species of Clematis are very closely 

 allied to the tendril-bearing Naravelia : the Fumariacese include 

 closely allied genera which are Leaf-climbers and tendril-hearers. 

 Lastly, one species of Bignonia is both a Leaf-climber and a tendril- 

 bearer t and other closely allied species are twiners. 



Tendrils of the second great division consist of modified flower- 

 peduncles. In this case Likewise we have man; interesting tran- 

 sitional states. The common Vine (not to mention the Gardio- 

 spermum) gives us every possible grade from finely developed 

 tendrils to a bunch of flower-buds, bearing the single usual lateral 

 flower-tendril. And when the latter itself bears some flowers, as 

 we know is not rarely the case, and yet retains the power of clasp- 

 ing a support, we see the primordial state of all those tendrils 

 which have been formed by the modification of flower-peduncles. 



According to Mold and others, some tendrils consist of modified 

 branches: 1 have seen no such case, and therefore of course 

 know nothing of any transitional states, if such occur. But Lo- 

 phospermum at least shows us that such a transition is possible ; 

 for its branches spontaneously revolve, and arc sensitive to con- 

 tact. Hence, if the leaves of some of the branches were to abort, 

 they would be converted into true tendrils. Nor is it so improbable 

 as it may at flrst appear that certain branches alone should become 

 modified, the others remaining unaltered; for we have seen with 

 certain varieties of Phaseolw that some of the branches are thin 

 and flexible and twine, whilst other branches on the same plant 

 are stiff and have no such power. 



If we inquire how the petiole of a leaf, or the peduncle of a 

 flower, or a branch first becomes sensitive and acquires the power 

 of bending towards the touched side, we get no certain answer. 

 Nevertheless an observation by Hofmeister* well deserves atten- 

 tion, namely, that the Bhoots and leaves of all plants, whilst 

 young, move after being shaken ; and it is almost invariably 

 young petioles and young tendrils, whether formed of modified 

 leaves or flower-peduncles, which move on being touched ; so that 

 it would appear as if these plants had utilized and perfected a 

 widely distributed and incipient capacity, which capacity, as 

 far as we can see, is of no service to ordinary plants. If we 

 * Quoted by F. Colm, in his remarkable memoir, "Contractile Gewcbe im 

 Pflanzenreichc," Abhand. dor Schlesiehen Oesell. 1861, Ileft i. S. 35. 



