164 CLIMBING PLANTS 



when the plant was allowed to run over glass the root- 

 lets emitted a slightly viscous fluid. Probably the 

 plant, having done so, reabsorbs the watery part of 

 the fluid, leaving the rootlet glued to the surface of the 

 support. 



The fourth and last class of climbing plants is the 

 twiners, that is, plants which wind their stems round 

 the support they require. When the seedlings of such 

 plants first appear, they behave in the manner common 

 to ordinary herbs ; but after two or three joints have 

 been formed, the seedling begins to bend and revolve, 

 seeking for support. When it finds this, it grows very 

 rapidly, winding its stem round and round the stake or 

 stem that it has found. It is remarkable that, while 

 the majority of twiners revolve from left to right that 

 is, against the sun and against watch-hands others 

 revolve with the sun, from right to left. Among the 

 majority are to be reckoned Convolvulus, Wistaria, 

 Berberidopsis, Stephanotis, and Aristolochia or Dutch- 

 man's pipe ; while the minority includes the hop, the 

 honeysuckle, Lapageria, and a few others. In all these 

 cases, and many others, the plant never varies from 

 the hereditary habit. Darwin devoted much attention 

 to this matter, and entered very fully into it in his 

 volume on Climbing Plants. He could find only 

 three species, all exotics, that ever twined in both 

 directions. 



' Solanum dulcamara revolves and twines in two directions ; 

 this plant, however, is a most feeble twiner. Loasa aurantiaca 

 offers a much more curious case. I raised seventeen plants ; 

 of these, eight revolved in opposition to the sun and ascended 



