20 
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 S H H 
HHSHSSHHS HHH 
S H H H H H S H H H H H H 
$ H S H S H H S H H H 
SHHHSHHSSSSHSSHH 
HSSSHSSSHSHHHSSS 
SHSSHHHHSSIISSSSHH H 
H H S S H S H 11/ S S S U 
H H H S H S H S S S S S S* I I H S I S 1 U S 
H H H SSSSHHSHSSHSSIISS S 
HHHHHHSSISSSSHSSSSSSH S 
HHH HHS SSI SHS SSS S 
HHHHHHSSSSISSSSISISSH I 
HHHHHHSSSISSI%DIISSSH H 
HHHHHSSSSS+DDDD U D U S S S S 
HHH H S S I • • ••• BUS S 
H H S H S S S I D ••••••• U 1 <S> S H H 
HHSHSIDD%+D+%D%D U I S S H 
HS>S>ISUU%mU%**m%DUUSSH 
S H S III • D • e • • /// H 
HHSHSSIII*D%*D%UISSHH 
H H H H S I I I I I U m • %D I I S S H H 
HHHHHSSSISIUD+IISSHHH 
HHH H S I 1ST U I U S H H H 
H S HS H S> S I S U I U I I I S S S H H H 
H H H H S S S S I • m - • U S cP H S H H H 
S H H H H H S S S I / • I S S H H H H H 
H S SSS U U S H H H 
H Healthy SHSHUTII S S S H H H H 
S Slight infestation S S IS ISSSHHHSH 
I Infested SSSHHSHHHSH 
U Unhealthy SSS SSS 
D Dying S H S H H S S 
% Dead H 
Fig. 2.— Phylloxera "spot" in Zinfandel 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 
