STEMS AND THEIR APPENDAGES. 61 



morphological characters, often changing and ser^^ng 

 different purposes. In many species of plants having 

 woody stems, like the Grape, Passion-flower and American 

 Ivy, the tendrils are really metamorphosed flower-stalks, 

 for while the larger proportion serve in assisting the 

 plant to climb and retain a position where the leaves 

 will be exposed to the light, a much smaller number on 

 the same plant may blossom and eventually become a 

 bunch of fruit; that is, a bunch of fruit on such plants is 

 merely a productive tendril. It is only a few — from one 

 to five — of the tendrils first formed on the young Grape- 

 canes of the season that are fruitful, all that are produced 

 later being unproductive or barren, possessing great 

 irritability, which causes them to cling to or twine about 

 any object with which they come in contact. The ends 

 of the tendrils of the plants under consideration are 

 divided, sometimes into several branches, as in the Ameri- 

 can Ivy, or into two or more, as in those of the Grape, 

 two being the most usual number in the latter, and these 

 not of the same length ; consequently, when both divisions 

 are fruitful, the bunch of grapes will be double, with one 

 side shorter than the other, the lesser bunch having the 

 technical name of ' 'shoulder. " If there are two short and 

 fruitful branches the bunch may be double-shouldered, 

 or if there is a greater number the bunch may be a cluster. 

 Such terms as single-shouldered, double-shouldered and 

 clustered bunches are employed by pomologists in de- 

 scribing the form of the bunch in the different culti- 

 vated varieties of the Grape. 



It very frequently occurs that only one division of the 

 tendril will be fruitful, as shown in figure 18, the other 

 remaining barren, winding around some convenient 

 branch or twig. That the tendrils are of the same nature 

 as other parts of the plant, the juices flowing through 

 them as actively as in the stem, is shown by the fact that 

 a fertile may be grafted upon an unfertile tendril. As 



