Ill 



mr. oarwin ON CLIMBING plants. 



avoid asking, whether the difference between foliar and axial 

 organs can be of so fundamental a nature as is generally sup- 

 posed to be the case*. 



We have attempted to trace some of the stages in the genesis 

 of climbing plants. But, during the endless fluctuations in the 

 conditions of life to which all organic beings have been exposed, 

 it might have been expected that some climbing plants would have 

 lost the habit of climbing. In the cases given of certain South 

 African plants belonging to great twining families, which in 

 certain districts of their native country never twine, but reassume 

 this habit when cultivated in England, we have a case in point. 

 In the leaf-climbing Clematis jlammula, and in the tendril-bearing 

 Vine, we see no loss in the power of climbing, but only a remnant 

 of that revolving-power which is indispensable to all twiners, and 

 is so common, as well as so advantageous, to most climbers. In 

 Tecoma radicans, one of the Bignoniacese, we see a last and 

 doubtful trace of the revolving-power. 



With respect to the abortion of tendrils, certain cultivated 

 varieties of Cucurbita pepo have, according to Naudinf, either 

 quite lost these organs or bear semi-monstrous representatives of 

 them. In my limited experience, I have met with only one in- 

 stance of their natural suppression, namely, in the common Bean. 

 All the other species of Vicia, I believe, bear tendrils ; but the Bean 

 is stiff enough to support its own stem, and in this species, at the 

 end of the petiole where a tendril ought to have arisen, a small 

 pointed filament is always present, about a third of an inch in 

 length, and which must be considered as the rudiment of a tendril. 

 This may be the more safely inferred, because I have seen in 

 young unhealthy specimens of true tendril-bearing plants similar 

 rudiments. In the Bean these iilaments are variable in shape, as 

 is so frequently the case with all rudimentary organs, being either 

 cylindrical, or foliaceous, or deeply furrowed on the upper surface. 

 It is a rather curious little fact, that many of these filaments 

 when foliaceous have dark-coloured glands on their lower surfaces, 

 like those on the stipules, which secrete a sweet fluid ; so that 

 these rudiments have been feebly utilized. 



One other analogous case, though hypothetical, is worth giving. 

 Nearly all the species of Lath yr us possess tendrils; but L. nissolia 

 is destitute of them. This plant has leaves, which must have 



* Mr. Herbert Spencer has recently argued ('Principles of Biology,' 1805, 

 p. 37 et seq.) with much force that there is no fundamental distinction between 

 foliar and axial organs in plants. 



t Annates des So. Nat. 4th series, Bot. torn. vi. 1856, p. 31. 



