But as the roots are very spreading it is important to stir the soil well but slightly and avoid deep plowing, for it is well known that through accidental injury to the roots the various "armillaria" enter the trees to develop the "pourridie" or "pus disease", or "circle disease". It is better, then, to use a rootstock immune to this malady so wide-spread among our native walnuts. _J. nigra_ enjoys this happy advantage of offering no foothold to this parasite, so harmful to its sister species. It accommodates itself well in many soils in which _J. regia_ will grow, even dry and gravelly, but prefers soils which are fresh, open, rich, and especially, deep. Its roots are long and vertical and their development stops in contact with an impermeable layer of soil. It produces specimens magnificent in height and rapidity of growth. Color of bark differs, though diameter of tree is more or less the same. This slight objection may be easily avoided by grafting regia on nigra at ground-level when wood is well matured and in mild weather. Proof that this species of walnut is resistant to "pourridie" was given in a report to members of the Congress of Grenoble in 1936 by Mr. Bourne of Saint Marcelin. "At Blache de Vinay, we are told, some black walnuts, planted more than thirty years ago in an infested field, have shown full resistance. One tree, grafted at ground-level and planted too deep, was infected many years ago by the "pus" above the graft on the _J. regia_ part. The diseased part was treated as was the custom then, with sulphuric acid, etc. The wound healed and the rootstock remained absolutely clean. A photo by Mr. Roy, Director of Agricultural Services at Isere, establishes this absolute proof. Other varieties of walnut have been tested as rootstocks--_cinerea_, _cordiformis_, and _Siebodiana_, but only the first seems to have given any satisfactory results. Reporter Bourne concludes, "The primary purpose of our research on rootstocks will be to obtain a hybrid of _regia_ x _nigra_ that will combine the resistance of nigra to the "pourridie" and regia's habit of vegetating late in spring. By virtue of the ability of the female element to transmit its rusticity and vegetative form it seems, _a priori_, that we shall get a good rootstock by crossing _nigra_ as mother by Franquette (sic) and then if need be, by backcrossing to Franquette in the second generation. There exists a 4th type of walnut graft, dating from 1880, which if done intelligently, permits the rapid multiplication of the walnut--the root graft.