Chap. m. POLEMONIACBiE. Ill 



But several times I watched cases like the following : 

 a tendril caught a thin stick by the hooks of one of 

 its two extreme branches; though thus held by the 

 tip, it still tried to revolve, bowing itself to all sides, 

 and by this movement the other extreme branch soon 

 caught the stick. The first branch then loosed itself, 

 and, arranging its hooks, again caught hold. After a 

 time, from the continued movement of the tendril, 

 the hooks of a third branch caught hold. No other 

 branches, as the tendril then stood, could possibly 

 have touched the stick. But before long the upper 

 part of the main stem began to contract into an open 

 spire. It thus dragged the shoot which bore the 

 tendril towards the stick; and as the tendril con- 

 tinually tried to revolve, a fourth branch was brought 

 into contact. And lastly, from the spiral contraction 

 travelling down both the main stem and the branches, 

 all of them, one after another, were ultimately brought 

 into contact with the stick. They then wound them- 

 selves round it and round one another, until the whole 

 tendril was tied together in an inextricable knot. 

 The tendrils, though at first quite flexible, after 

 having clasped a support for a time, become more 

 rigid and stronger than they were at first. Thus the 

 plant is secured to its support in a perfect manner. 



Leguminos^. — Pisum sativum. — The common pea 

 was the subject of a valuable memoir by Dutrochet,* 

 who discovered that the internodes and tendrils 



* Comptes BenduB, torn. xvii. 1843, p. 989. 



