Chap. V. CONCLUDING REMARKS. 199 



present the most complete identity in their several 

 characteristic powers. Tendrils of both kinds sponta- 

 neously revolve at about the same rate. Both, when 

 touched, bend quickly to the touched side, and after- 

 wards recover themselves and are able to act agaiu. 

 In both the sensitiveness is either confined to one side 

 or extends all round the tendril. Both are either 

 attracted or repelled by the light. The latter property 

 is seen in the foliar tendrils of Bignonia capreolata 

 and in the axial tendrils of Ampelopsis. The tips 

 of the tendrils in these two plants become, after con- 

 tact, enlarged into discs, which are at first adhesive 

 by the secretion of some cement. Tendrils of both 

 kinds, soon after grasping a support, contract spirally ; 

 they then increase greatly in thickness and strength. 

 When we add to these several points of identity the 

 fact that the petiole of Solanum jasminoides, after 

 it has clasped a support, assumes one of the most 

 characteristic features of the axis, namely, a closed ring 

 of woody vessels, we can hardly avoid asking, whether 

 the difference between foliar and axial organs can be 

 of so fundamental a nature as is generally supposed ? * 

 We have attempted to trace some of the stages in 

 the genesis of climbing plants. But, during the 

 endless fluctuations of the conditions of life to which 

 all organic beings have been exposed, it might be 

 expected that some climbing plants would have lost 



* Mr. Herbert Spencer has much force that there is no fun 

 recently argued (' Principles of damental distinction between the 

 Biology,' 1865, p. 37 et seq.) with foliar and axial organs of plants. 



