ACADEMY OF SCIENCES. 125 



time for applying it should be during the month of April, as at this season the 

 insects that have survived the winter have not begun to lay their eggs, and 

 experiments that have been carried on during the summer show that while the 

 bisulphide is a certain poison to the insect in all its forms it does not destroy 

 the egg. This is the reason of its reported failure in France, where probably 

 it was not applied at the right season. By using it in the spring, at the time 

 that the winter eggs at the surface are being hatched and before the hyber- 

 nating form has commenced laying, we have the insect entirely in (hat phase 

 of its existence in which it can be killed by the bisulphide; and experience 

 has shown that at this time its destruction is completed by one application of 

 the poison. The only place where the insect has been found on some few of 

 the vines treated has been near the surface, where the vapor became too much 

 diluted with the air to prove fatal, and one patch of the insect was found at a 

 depth of more than four feet, where it was possible the vapor had not pene- 

 trated. In the course of my experiments I have discovered that the refuse 

 lime from the gas works will kill the insect for some distance beneath the sur- 

 face when it has been applied round the roots, and from what we know of the 

 natural history of the insect it is almost certain that it will shortly die out at 

 any great depth, when it cannot be renewed by fresh nymphs developed from 

 the winter ova. The plan of treatment I have advised for the diseased vines 

 is, during the winter, and as late as possible before the cessation of the rains, 

 to apply three or four pounds of the lime refuse round the stem, drawing the 

 earth away from the stem to the depth of two or three inches, at the same 

 time brushing the stem for six or eight inches above the ground with train oil. 

 Then about the middle of April to the first week in May use the bisulphide of 

 carbon under ground in the way I have pointed out, making three holes round 

 each vine at a distance of eighteen inches from the stem, and using about two- 

 thirds of an ounce to each hole, the holes when the tube is withdrawn being 

 well filled with earth and stamped down. 



When the vine is so far diseased as to have suffered materially in its foliage, 

 the better plan is, I think, to pull it up. But a careful examination will de- 

 tect the presence of the insect on the roots of vines the foliage of which ap- 

 pears quite healthy and which are bearing a full crop of fruit. In this stage 

 of the disease the insect is not in sufficient numbers to so completely absorb 

 the descending sap as to have prevented the formation of new rootlets, and 

 while this is the case the vine can readily recover itself. Whatever may be 

 the case in other countries, I am convinced that here the destruction of the 

 lower portion of the roots is not caused by the direct attack of the insect, as I 

 have found the roots dead two or three feet beyond where any traces of the in- 

 sect could be discovered. Owing to the peculiarities of our climate, the vines 

 send their roots much deeper here than in Europe, and although in the older 

 vines in the vineyard where I investigated the disease the roots derived* their 

 principal supply of nourishment at depths from six to ten feet, I have not 

 found the phylloxera at a greater depth than four feet, although the roots 

 were dead as far as they could be traced, and far beyond any part that had 

 been directly attacked by the insect. Where the vines are pretty badly dis- 

 eased, I think the application of the bisulphide at the beginning of the winter, 



