38 TWINING PLANTS. Chap. I. 



thev were enabled to twine round trunks of trees, for 

 they could not grow tall enough in a single season to 

 reach the summit and gain the light. 



By what means certain twining plants are adapted to 

 ascend only thin stems, whilst others can twine round 

 thicker ones, I do not know. It appeared to me 

 probable that twining plants with very long revolving 

 shoots would be able to ascend thick supports ; accord- 

 ingly I placed Ceropepia Gardnerii near a post 6 

 inches in diameter, but the shoots entirely failed to 

 wind round it ; their great length and power of move- 

 ment merely aid them in finding a distant stem 

 round which to twine. The Sjrfiterostemma marmora- 

 tum is a vigorous tropical twiner ; and as it is a very 

 slow revolver, I thought that this latter circumstance 

 might help it in ascending a thick support ; but though 

 it was able to wind round a 6-inch post, it could do 

 this only on the same level or plane, and did not 

 form a spire and thus ascend. 



As ferns differ so much in structure from phanero- 

 gamic plants, it may be worth while here to show that 

 twining ferns do not differ in their habits from other 

 twining plants. In Lygodium articulaium the two 

 internodes of the stem (properly the rachis) which 

 are first formed above the root-stock do not move ; 

 the third from the ground revolves, but at first very 

 slowly. This species is a slow revolver : but L. 

 seandens made five revolutions, each at the average 

 rate of 5 hrs. 45 m. ; and this represents fairly well the 

 usual rate, taking quick and slow movers, amongst 



