THE GRAPE PHYLLOXERA IN CALIFORNIA. Ill 



from a single wanderer. Similarly, it is possible that the infesta- 

 tions on vines 11 and 12 originated with one individual each. 



In all of four inoculated vines the infestations were confined to 

 the larger roots, and there was no nodositous infestation such as oc- 

 curred with wanderer inoculations in potted vines at the laboratory. 

 This is explained by the fact that the soil in the cans did not crack 

 deeply enough to reach the rootlets (none of which came near the 

 soil surface) while it cracked badly around the base of the stems of 

 the vines. It is therefore most probable that the wandering larvse 

 passed down the vine stem. Cracks of 1 foot or more in depth were 

 quite abundant in the vineyards in July and August, and it was 

 possible to find rootlets such as form nodosities when punctured by 

 phylloxera? at a depth of 6 inches from the soil surface. At that 

 time of year there is generally in the vineyards a wide crack about 

 the base of the vines, and it is through these cracks that the great 

 majority of the wandering larvse ascend to the surface. In the vine- 

 yard a wanderer could never be kept under observation long enough 

 to be sure that it entered a crack permanently, therefore, with the 

 purpose of seeking a root. Wanderers readily enter any crack which 

 they can not bridge but frequently reappear after a short period 

 of time. In pots they have been observed to enter whatever cracks 

 they encountered, subsequently inoculating roots buried below. In 

 other experiments with pots the wandering larva? have been found 

 to crawl down the crack between the soil and the inner side of the 

 pot and inoculate the rootlets growing around the inside of the pots. 

 Also it has been observed that in the vineyard experiments the inoc- 

 ulation was probably made by the wanderers crawling down the 

 stem, since no other available cracks were favorable. In the vine- 

 yard, therefore, it is assumed that the wanderers enter the first crack 

 they encounter. 



In the experiments of 1914 with sticky papers, wandering larvae 

 were captured at varying distances up to 5 feet from the nearest 

 infested vine. The four inoculated vines the year following were 

 2, LJ, 1§, and 5 feet, respectively, from the nearest infested vines. 

 It should be said that there was a possibility that the infestations 

 were inoculated by wanderers coming from infested vines at a greater 

 distance. In the instance of the three inoculated vines planted in 

 cans around one single vineyard vine it is reasonably certain that 

 all three became inoculated from the central vine. From this vine 

 large numbers of wanderers were observed to issue. 



No vines were planted more than 5^ feet away from a vineyard vine, 

 the vineyard being planted 8 by 8 feet. 



The soils used in the cans were of different types, but no satisfactory 

 conclusions were drawn from this feature. It was noted that the 



