THE GRAPE PHYLLOXERA IN CALIFORNIA. 107 



later observations showed that wanderers were no more abundant on 

 fertilized than on check, unfertilized vines. On young vines in 

 pots wanderers were often observed to ascend the vine stalks to 6 

 inches above the soil surface, and in one instance on an American 

 nonresistant vine (Golden Champion) several of them fastened on 

 the bark and matured there (1914). This vine was never exposed 

 to the brightest light and, moreover, during 1914, within a radius 

 of 4 inches from its stalk was placed a glass cylinder, around the 

 bottom of which was fastened 2 inches of black paper, so that the 

 stem of the vine received little light. In 1915 the glass cylinder 

 and black paper were removed and no wanderers settled on the aerial 

 portion, although from June 29 to September 10 a limited number 

 of them could be seen almost daily ascending the stalk to about 6 

 inches as in the previous year. 



During 1913 and 1914 many instances were observed of wanderers 

 infesting the rootlets in the pots used in the cages for observations 

 on living vines (Pis. V-VII). In these cases the wanderers were 

 produced on the exposed portions of the roots, and wandering off 

 these, they found themselves on the surface of the soil in the pots. 

 They then proceeded to pass down through the cracks around the 

 inside periphery of the pot, where the soil had dried, and finally 

 reached the rootlets growing against the inside of the pot. Such 

 infestations occurred on rootlets from the surface to the total depth 

 of 9 inches. This infestation occurred during July, August, and 

 September, and in November, when the vines were pulled up, most 

 of the nodosities produced by the phylloxeras had rotted. In some 

 cases rootlets appeared above the soil around the periphery of the 

 pot, and these were infested easily and abundantly through the 

 agency of wandering larvae. In the pots in which quartz had been 

 substituted for earth for experiments with fertilizers, the wanderers 

 were able to find their way down to the rootlets, although the cracks 

 in the quartz were fewer and narrower than in the earth. It may 

 be mentioned that the earth used in the pots in 1913 was a rather 

 heavy dark loam, mixed with sandy loam, and in 1914 only the 

 heavy dark loam was used. A layer of gravel and sand about one- 

 fourth inch thick was laid on the surface, but this did not prevent 

 cracking around the inside periphery of the pot. The heavier soil 

 of 1914 seemed to allow of easier passage for the wanderers. 



In the spring and summer of 1914 three vine section cages con- 

 taining cuttings were placed together in a trench. Two of these were 

 infested with phylloxeras throughout May and June. On July 18 

 it was found that a vine in the third cage was infested with two egg- 

 laying adults, each situated on a nodosity. The vines in this sec- 

 tion cage never had been inoculated, and it is certain that their in- 



