60 GRAPE CULTURE AND 



varieties, one producing the gall type and not specially 

 adapted to the root type, and the other producing all forms 

 of the root type with great ease and during the longest 

 period, but in no case bearing galls. Nearly all the observa- 

 tions in the past have been taken from this vine. It still 

 remains strong and vigorous. 



DANGER OF SPREADING BY THE WINGED FORM. The fact 

 that the winged form, so far as it appeared in considerable 

 numbers, was limited to a single vine in our vineyard plot, 

 necessarily diminishes greatly the probability of its spreading 

 to any other vineyard district from this place, and by this 

 form. If all the vines were equally productive of the winged 

 insect, the probabilities for infection would certainly be 

 greatly multiplied; but there would still be great doubts as to 

 whether they would be carried to any great distance and find 

 lodgment in a spot where the proper conditions for continued 

 life obtain. The winged insects have mostly been found 

 crawling upon the ground quite near the vine, being thus pro- 

 tected by the foliage above them from the winds which might 

 otherwise take them up into the air and transport them to 

 other districts. A few scattering ones only have been found 

 on the foliage, but the thick screen of trees and the ranges of 

 high hills in the direction of the regular winds prevailing at 

 their time of development, renders any actual danger from 

 this source exceedingly remote. 



COMPARISON OF EASTERN AND CALIFORNIA TYPES. 



As a basts for comparison of the forms which have come 

 under our notice with those known to exist elsewhere, I in- 

 sert the following tabulated arrangement of the various forms 

 which this insect may assume, as presented in a report by 

 Professor Riley. It shows at once the complexity of its forms, 

 and the diversity of its habits: 



I. The gill-inhabiting type, forming galls on the leaves, 

 and presenting: 



