ON THE ORIGIN AND PECULIARITIES OF CLIMBING PLANTS. 141 



ON THE ORIGIN AND PECULIARITIES OF 

 CLIMBING PLANTS. 



By Rev. Prof. G. Henslow, M.A., V.M.H., &c. 



[Abstract of Lecture given on October 9, 1906.] 



An abstract of a lecture on " How Plants Climb," delivered to the students 

 at theChiswick Gardens, June 1901, is reported in this Journal (vol. xxvi.), 

 so that there is no need to reproduce the same details ; but I would wish to 

 illustrate three features more fully. The origin of certain climbers is 

 there suggested to be due to overcrowding and the consequent obscurity. 

 With regard to this Professor Warming has some interesting observations 

 on the plants of Lagoa Santa, Brazil. He writes as follows on the 

 genesis of tropical lianes : — " Twining and clasping climbers are a product 

 of forests with deep shade. The evolution of these plants will have been, 

 without doubt, thus : Germinating in the shade the young plant is forced 

 to grow in height, and its branches, to elongate, and become slender. The 

 first step is seen in the plants lying simply upon the boughs of the shrubs 

 and trees. These * sarmentous ' climbers are numerous in the flora of 

 Lagoa Santa, e.g. Chamissa, Goinphorena, &c. The second step, already 

 marked by signs of adaptation, is very clearly pronounced, in which the 

 branches spread out at right angles to the axis, so that they rest with 

 more ease and security upon other plants. The third step is seen in 

 twiners in which the circumnutation assists ; but in a general way 

 adaptations of a morphological kind are rare. The fourth step is repre- 

 sented by clasping, provided with a special apparatus. In this category, 

 at the bottom of the scale, are sjpiny climbers ; at the summit are plants 

 with tendrils and sensitive organs of adhesion." 



M. Costantin in his work on " Tropical Nature " * alludes to M. Schenck's 

 study of lianes, who similarly observed how species Living in the open 

 were non-climbers, but when within a forest became climbers. He 

 mentions Fuchsia integrifolia occurring both, in the forests of the moun- 

 tains of Brazil, where it climbs to a height of three metres, and outside 

 on rocky ground where it forms bushes about 5 to 6 feet in height. He 

 considers the former to have been derived from the latter, as two other 

 species of Fuchsia in Brazil are bushes like so many others. As another 

 case he mentions Hebanthe holosericea (ord. Amarantacece). 



This conclusion is corroborated by experiments. So far as I know, 

 the great, surgeon J. Hunter first called attention to the fact that if seeds 

 of non- climbing plants be allowed to germinate in the dark and be 

 provided ^Aih a stick they become climbers. In his " Memoranda on 

 Vegetation" he thus writes: — "On Creepers, Climbers, dingers, and 

 Twisters. — It would appear that weakness in anything that has powers 

 of action within itself, produces or stimulates the parts, so weak, to take all 

 advantage of collateral support. Even a bean, which when strong seems 

 * La Nature Tropicale, p. 84. 



