LEAVES 



37 



lobed,, while those of V. candicans are more often than not entire. 

 The lobing of grape foliage is characterized by several special 

 terms (Fig. 24). The depression between adjoining lobes is 

 called a sinus; a sinus at the apex of a leaf is terminal; at the 

 base of the sides of the leaves hasal, which, however, must not 

 be confused with the petiolar sinus in which the petiole is 

 attached to the leaf. 

 The sinuses may be of 

 various widths and 

 depths and may be 

 closed or overlapping. 

 The lobes may be 

 acute, obtuse, ov acicmi- 

 71 ate. 



61. Leaf surfaces. — 

 The surfaces of the 

 leaves of grapes and 

 the small-fruits de- 

 mand attention. The 

 two surfaces are usu- 

 ally different in color; 

 the upper one is most 

 often glabrous while 

 the lower is usually pu- 

 bescent. In the grape 

 the character of the pu- 

 bescence is often typi- 

 cal of a species and 



may be hairy, woolly, downy, or cohivehhy. Vitis Lahrusca is 

 characterized by leaves densely pubescent beneath, whitish at 

 first but dun-colored on mature leaves. The lower surface of the 

 leaves of V. hicolor is glabrous but heavily covered with bloom, 

 which, on the green of the leaf, seems light blue. The pubescence 

 on the lower surface of leaves of V. cestivalis is reddish or rusty. 



62. The leaves of brambles. — The leaves of the bramble-fruits 

 furnish character on which divisions into species may be made. 

 Besides the number of leaflets, their size, shape and color, the 

 surfaces of the leaflets of some species are smooth, of others 

 wrinkled, plicate, or rugose. In some species the margins are 



Fig. 24. Leaf of Niagara grape, a. petiolar 

 sinus ; b. basal sinus ; c. lateral sinus. Pal- 

 mately veined : five lobed ; petiolar sinus 

 deep ; basal sinus shallow ; lateral sinus 

 deep ; teeth coarse and broad. 



