THE GRAPE PHYLLOXERA IN CALIFORNIA. 21 



their wood growth than do healthy ones. Such grapes mature, how- 

 ever, without attaining a good size or their normal saccharine con- 



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Fig. 3.— Phylloxera "spot" in Zinfandel vineyard, charted in 1915. Same "spot" 

 as shown in figure 2. (For description see test.) 



tent. Stunted vines produce leaves of a more uniform size than 

 healthy vines, and because the internodes of the canes are shorter, 

 the leaves appear more closely grouped, giving the "cabbage-head"' 





