. STEMS 



57 



Fig. 29. Coiling of 

 Petiole of Dwarf 

 Tropseolum. 



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

 of tendrils are very interesting subjects for st.udy, but they 

 cannot usually be managed very well in the schoolroom, 

 jj Continued observation soon shows that the tips 

 I of tendrils sweep slowly about in the air until 

 they come in contact with 



some object about which 

 they can coil themselves. 

 After the tendril has taken 

 a few turns about its sup- 

 port, 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. 28. Some tendrils are leaves or 

 stipules, others are modified stems. 



75. Twiners.^ — Only a few of the 

 upper intemodes of tlie stem of a twi- [ij- 

 ner are concerned in producing 

 the movements of the tip of the 

 stem. This is kept revolving in 

 an elliptical or circular path un- 

 til it encounters some roughish 

 and not too stout object about 

 which it then proceeds to coil 

 itself. The direction of the coil- 

 ing varies in different kinds of 

 climbers, some following the course shown in the figure 



Fig. 30. Twining Stem 

 of Hop. 



1 See article on Climbing Plants, by Dr. W. J. Beal, in the American Nat- 

 uralist, Vol. IV, pp. 405-415. 



