46 



ELEMENTS OP BOTANY. 



(2) Laying hold of objects by means of tendrils or twining 

 branclies or leaf-stalks, as shown in Figs. 30, 31. 



(3) Twining about any slender upright support, as shown 

 in Fig. 32. 



69. Tendril-Climbers. — The plants which climb by means 

 of tendrils are very interesting subjects for study, but they 

 cannot usually be managed very well 

 in the schoolroom. Continued obser- 

 vation soon shows that the tips of 

 tendrils sweep slowly about in the air 

 until they come in contact with some 

 object about which they can coil them- 

 selves. After the tendril has taken a 

 few turns about its support, the free 

 part of the tendril coils into a spiral 

 and thus draws the whole stem toward 

 the point of attachment as shown in 

 Fig. 30. Some tendrils are leaves or 

 stipules, as shown in Fig. 90 ; others 

 are modified stems. 



70. Twiners. — Only a few of the 

 upper internodes of the stem of a 

 twiner are concerned in producing the 

 movements of the tip of the stem. 

 This is kept revolving in an elliptical 

 or circular path until it encounters 

 some roughish and not too stout object, 

 about which it then proceeds to coil 

 itself. The direction of the coiling varies in different kinds of 

 climbers, some following the course shown in the figure of the 

 hop on the next page, others, as the morning-glory, taking 

 the opposite course. 



71. Underground Stems. — Stems which lie mainly or wholly 

 underground are of frequent occurrence and of many kinds. 



Fiu. 30. — Coiling of a Ten- 

 dril of Bryony. 

 iCjportion coiled around a twig; 

 w, w', places where direction 

 of coiling reverses ; u, un- 

 coiled portion of tendril. 



