502 



PHYSIOLOGY OF GROWTH. 



unable to attach themselves in the manner typical of the tendrils 

 of many Cucurbitaceee and the tendrils of Vitis. On the other 

 hand, the ends of the tendril branches have the power of pro- 

 ducing attachment balls. When, viz., their tips come into contact 

 with the stone or woodwork against which the plant is growing, 

 they at once begin to swell, as a result of the contact stimulus, so 



FIG. 167. Tendril of Ampelopsis quinquefolia 

 unattached. 



FIG. 168. Tendril of Ampelopsis 

 quinquefolia, with attachment balls. 



as to form the attachment balls. The cells of these last exude a 

 viscid secretion, by means of which the attachment of the tendril 

 tips is effected. In Fig. 168 is drawn a tendril of Ampelopsis, 

 which was removed from a wooden wall after the tips of its 

 branches had just began to form attachment balls. If an Ampe- 

 lopsis tendril has in this way fixed itself, there are produced in 

 the part of the tendril between the points of attachment and the 

 plant spiral windings. The development of these, as in tendrils 

 of Sicyos, Vitis, etc., is due to propagation of stimuli, and is inti- 



