8 BULLETIN" 903, U. S. DEPARTMENT OF AGRICULTURE. 
Infestation from accidental distributing centers may be avoided 
by strictly enforced quarantine measures. 
Accidental spread has been the main cause of most of the phyllox- 
era infestation throughout the vineyards of California because of 
its being an initial inoculation, developing later into a center of 
natural dissemination. 
A general survey of the growth of the grape industry, which 
at times, as in the late eighties and early nineties, attained the 
proportion of a boom, furnishes an indication of the accidental 
spread which took place concurrently. 
Cuttings were used almost exclusively for planting vineyards in 
preference to rooted vines, the latter being used for replanting 
" misses." and even then not commonly used. As will be shown 
later, there is little, if any. danger in disseminating the phylloxera 
from cuttings, unless these are heeled in in infested soil while await- 
ing shipment. It is for this reason that the accidental diffusion 
was greatly restricted. If rooted vines had been commonly used, 
originating from the same district as the cuttings, the accidental 
diffusion would have been so general as perhaps to have precluded 
before long the growing of vinifera vines on their own roots. 
THE WINGED MIGRANT NOT A FACTOR IN SPREAD UNDER CALIFORNIA 
CONDITIONS. 
Profiting by the investigations and experiments that were being 
carried on in France, the University of California in conjunction 
with the State Board of Viticulture made extensive efforts to ar- 
rest the ravages of the phylloxera, and made investigations pertain- 
ing to its life history and habits. These deserve special mention 
in this report. 
Dr. F. W. Morse (16) of Oakland. Calif., during the period 
1881-1856. as an assistant in the General Agricultural Laboratory. 
discovered in the course of his investigations on August 26. 1SS4. 
specimens of the gall louse or leaf -inhabiting form of the phylloxera. 
As is noted under the heading " The galiicole and its relation to 
California conditions " (p. 95 I . this is the only recorded instance 
of the finding in California of the leaf galls. In this connection it 
may be said that in the experimental vineyards of the Bureau of 
Plant Industry, United States Department of Agriculture, in which 
are collected many varieties and hybrids of species of American 
vines, not a few of which are susceptible to leaf galls when culti- 
vated in the Eastern or Middle States, au exceptionally good field 
for observation is offered. Mr. G. C. Husrnann. under whose direc- 
tion these vineyards are conducted, states that the leaf gall, to his 
knowledge, has never been found in them. Extensive correspondence 
