THE GRAPE PHYLLOXERA IN CALIFORNIA. 97 



Gloire de Montpellier. The infested foliage had an abundant sup- 

 ply of newly hatched larvae, but in no case did the inoculation suc- 

 ceed. It is possible, however, that many of the larvae of such a late 

 generation had radicicole characteristics, and therefore none such 

 would settle on the leaves. Both of the foregoing series of inocula- 

 tions were made under conditions of light atmospheric humidity. 

 Recent research in Italy (11, p. 335-345) (17) shows that in that 

 country, at least, humidity and irrigation have much influence in the 

 production of galls on resistant vines. Both the Riparia X Rupestris 

 3309, and the Rupestris St. George are said by Panatelli to produce 

 many galls in dry locations. It appears, however, that in general 

 a greater humidity is conducive to the production of gallicoles on 

 resistant vines and their hybrids. Thus out of 24 well-known resist- 

 ant varieties enumerated by Panatelli, 21 produced many galls and 

 3 few galls in humid localities, while in dry locations 10 produced no 

 galls, 5 few galls, and 9 many galls (17). In this connection, it may 

 be added that in California resistant vines have been frequently 

 observed growing among badly infested viniferae and never showing 

 any sign of gall infestation. On no occasion, indeed, have the writers 

 ever observed phylloxera galls in California, and there is only one 

 authenticated case in California of gallicoles, that being the discovery 

 in August, 1884, by Dr. F. W. Morse (16), of gall-inhabiting phyl- 

 loxerae on a Canada (labrusca X riparia X vinifera) vine on the 

 University of California grounds at Berkeley. 



The two shipments of gallicoles cited above were also used in 

 experiments to determine whether this form would live on roots. 

 On July 16, 1913, 75 newly hatched gallicoles were placed on two 

 pieces of severed root (Zinfandel) in a petri dish in the cellar. On 

 a third smaller root 100 eggs from the galls were located. On 

 August 18, on the two larger roots, five phylloxerae with the typical 

 radicicole characteristics matured. On September 3 there were 

 altogether seven mature egg-laying radicicoles, of which six had 

 matured on the two larger roots. Thus out of 100 eggs and 75 newly 

 hatched larvae only seven phylloxerae matured. 



On September 6 a similar experiment was begun on severed roots 

 in the cellar. On two roots 75 eggs apiece were placed. These all 

 turned black and none hatched, it appearing that the embryo suffered 

 injury through fermentation that developed during the transconti- 

 nental journey. This supposed fermentation did not affect the larvae 

 already hatched and which were used for the foliage experiment. 



A further experiment took place on roots of a living vine (Thomp- 

 son's Seedless) which was inoculated July 16 with 50 eggs. Three 

 insects from this inoculation matured August 12, 13, and 14. They 

 were typical radicicoles and laid eggs at the rate of between two and 

 1900°— 21 7 



