Cuap. 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 again. 
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. 
