600 [ DISEASES OF THE VINE. 



the American vines on which to deposit the eggs from 

 which are born the male and female individuals which in 

 their turn produce the fertilized winter egg. Should 

 there be no American vines in the neighbourhood the 

 winter egg laid on the stem of the European vine 

 hatches ali the same, but the larva (foimdress larvji or 

 moth.r larva] is rarely able to produce the typical 

 gall on the foliage of the European vine, in order 

 to renew the life- cycle. Should this take place, the 

 young produced within the original gall instead of 

 proceeding to form new galls on the foliage, descend 

 to the roots where they multiply with great rapidity. 

 It is therefore supposed that in the case of the 

 European vine the spread of Phylloxera takes place 

 chiefly by means of the larvae, of the roots and 

 rootlets, hybernating during the winter, and spreading 

 slowly from root to root, mostly underground in sandy 

 and porous soils, or coming to surface ;md descending 

 again on the roots through the fissures of the soil in 

 clayey or heavy lands. These larvae are also transported 

 from one vineyard into another along with the feet or 

 induments of workmen, on the implements used in tillage, 

 by means of primings, manure, by the action of wind and 

 rain, of running water, by the animals employed in tilling 

 the land or in carrying the produce, by plants or other 

 produce to which infected soil is attached, and in many 

 other ways The activity of the /a? vae on the roots is 

 at its height in spring and early summer, but after June 

 this activity slows down gradually, to almost a complete 

 standstill in winter. 



On the rootlets the Phylloxera provokes the forma- 

 tion of tubercles or galls, and at the growing end of the 

 rootlet are produced nodosities, generally of a character- 

 istic hooked shape. These formations interfere seriously 

 with the functions of the rootlets, and when sufficiently 

 numerous the physiological function of the roots is totally 



