54 



THE STEM 



39. The stem aud leaves of Galivm, or 

 Bedstraw, studded with backward 

 pointing hooks (magnified). 



Galium (Fig. 39), catching on leaves and branches, pre- 

 vent these climbers from slipping from their supports. 



If we attempt to pull 

 a tangle of Galium away 

 from the foliage of the 

 herbs and shrubs over 

 which it runs, the plant 

 itself is torn in pieces 

 before we succeed in 

 dislodging it. 



77. Of special organs 

 for climbing, the clinging 

 rootlets of the Trumpet 

 Creeper have already 

 been described. Leaves, aiid parts of leaves serving the 

 same general purpose, but adapted in a much more 

 remarkable manner to a climbing habit, will be described 

 in the next chapter. In the list of specialized climbing 

 organs there still remain certain stems, modified into 

 either adherent or twining tendrils. 



78. Adhesive disks. — The Virginia Creeper illustrates 

 the first case. The tips of certain branches are flattened 

 into disks with an 

 adhesive face (Fig. 

 40). This is applied 

 to the supporting 

 object, to which it be- 

 comes firmly glued. 

 Then a shortening 

 of the branches by 

 coiling brings up the 

 growing shoot close 

 to the support. This is an adaptation to climbing mural 

 rocks and walls or the trunks of trees, to which the 

 vine would not be able to cling by means of twining 

 tendrils. 



79. Twining tendrils. — Some tendrils are leaves or parts 

 of leaves, as those .of Cobcea (Fig. 73). The nature of a 



40. Tendrils of Virginia Creeper. 



