66 GRAPH CULTURE AND 



Santa Rosa, and were identified by Professor Hilgard to be 

 of the infertile variety. These are the only individuals of the 

 sterile variety found thus tar, and they came from rather large- 

 sized woody roots, such as are usually found near the sur- 

 face in ordinary California summers. May we not reasonably 

 conjecture that the unusual summer rains of 1884, causing arc 

 unusual abundance of white surface roots, have also been in- 

 strumental in developing exceptionally the normal fertile 

 winged form ? 



Mode of attack on Different Vines. There is one point 

 worthy of note as throwing some light upon the resisting power 

 of vines; it is the manner of the insects' attack. In the com- 

 mon vinifera even, they show preference for particular spots 

 on the roots, selecting those places where the bark is softest,, 

 usually near a crack. From this they extend upward and 

 downward along the line where the tissue is continuous from 

 that spot; and scarcely ever do we find them working at right 

 angles from this line. When the sap begins to ooze out and 

 rotting sets in, they precede it closely, always leaving a num- 

 ber of insects to continue the destruction until the spot be- 

 comes completely rotted and gives out no more sap. Large 

 numbers of insects will often be found feeding upon such 

 spots, apparently reluctant to leave them as long as any sus- 

 tenance can be derived therefrom. So closely is this mode 

 of working followed, that on many old Mission vines they 

 will be found only on a single spot, while the remainder of the 

 root is free from them. A root covered with a fuzzy bark is 

 noticeably objectionable to them, a harder one with cracked 

 or loosened bark is preferred. 



U-pon a thoroughly resistant stock the insects act quite dif- 

 ferently. They are usually scattered about, apparently at a 

 loss to know just where to begin operations. Their first 

 piercings are made, and instead of a .deep rotting which com- 

 pletely kills the bark to the woody tissue, a slight, thin black- 



