20 BULLETIN 903, U. S. DEPARTMENT OF AGRICULTURE. 



the susceptible varieties stand out the more vigorous vines of the less 

 susceptible kinds or even individuals of the same variety. 



HHH S S S 8 H H 

 H H S H S S H H S> H H H 

 8 H H H H H 8 H H H H H H 

 8 H8H 8HH 8HH H 

 8HHH8HH8888H8 8HH 

 H 8 8 S H 8 S8H8HHH8 8 S 

 SHSSHHHHSSIISSSSHH H 

 H H 8 8 H 8 H I If 8 8 8 U 



HHH8H8H88888 8IIH8ISIU 8 

 HHH8888HH8H8SH88II8S 8 

 HHHHHHS>8IS'8S8H8tfSSS > S>H 8 

 HHH H H 8 881 8 H 8 8 8 8 8 

 HHHHHHS8S8/8888I8 788H I 

 HHHHHH888I88I%D I I 8 S 8 H H 

 HHHHHS88SS9DDDD U D U S S 8 8 

 HHH H 8 8 / • • • • • D U S> 8 

 HH8H888IDmm**m*%UI 8SH H 

 HHSHSIDD+mD%+DmD U I 8 8 H 



Hs>s>is>(ju%mumm%%mDuu<s>s>H 



8 H 8 III • D m • • • III H 



H H S H 8 8 I I I • D • • D • U I 8 lP H H 



H H H H 8 I I I I I U * % % D I I 8 8 H H 



HHHHH888I8 I U D • / / 8 8 H H H 



HHH H 8 I I 8 I U I U & H H H 



H 8 H 8 H 8 8 I 8 U I U I I I 8 8 8 H H H 



H H H H 8 8 8 8 I *m*C/S8H8HHH 



8 H H H H H 8 8 8 I /# / J> 8 H H H H H 



H 8 8 8 8 U U 8 H H H 



H HtfiLTHY 8 H 8 H U I I I 8 8 8 H H H H 



8 Slight imesmioN 8 8 18 I888HHH8H 



I Ihtested 8 8 SHH8HHH8H 



U l/NHMLTHf 8 8 S 8 S> 8 



D Dying 8 H 8 H H 8 8 



• Dcm H 



Fig. 2.— Phylloxera "spot" in Zinfantlel vineyard, charted in 1914. (See text.) 



The year previous to showing a marked decline, vines frequently 

 bear an unusually abundant crop of grapes, and stunted vines seem 

 to produce a larger amount of grapes in comparison to the size of 



