16 



SYSTEMATIC POMOLOC'Y 



Gooseberries liave from one to tliree spines at the base of the leaf 

 witli occasional sniaUer ones ah)ii}j: tlie stems. In American cul- 

 tivated varieties, the spines are sliortci', usually borne singly, and 

 are scattered without order alonjj: tlie stem. 



24. Tendrils. — Some plants have highly specialized leaves or 

 branches which aid them in climbing. Whether a tendril is a 

 modified leaf or branch is known by its position. The only fruit 

 with which this text is concerned having tendrils is the grape, 



Fig. 9. Fruiting shoot of Vitis vulpina showing discontinuous tendrils. 



the tendrils of w^hich are modified branches since they either 

 arise in the axils of leaves or terminate stems. The tendril is one 

 of the organs most used in determining species and varieties of 

 grapes. Thus, in Vitis Lahrusca there is a tendril, or an in- 

 florescence, opposite every leaf on a fruit shoot, but in all other 

 species there are two leaves Avith a tendril opposite each and then 

 a third leaf without a tendril. In the first case the tendrils are 

 said to be coniimious (Fig. 8) ; in the latter, intermittent (Fig. 

 9). In the many species of grapes, tendrils may be long or short; 

 stout or slender; simple, hifurcaied, or trifurcated; smooth, 

 pubescent, or warty. To study tendrils of grapes properly, it 

 is necessary to have vigorous, healthy, typical canes from 

 mature plants. 



