Now it appears that _Phylloxera_ has long been in the habit of doing damage to vines in America, where, however, it attacks the leaves, on which it makes pocket-like galls, rather than the roots. Moreover, there are species and varieties of American vines which, even when planted in Europe, do not suffer at all from this insect at the roots, either because the rootlets do not push out at the same season as those of the European form, or because they form wood more rapidly and completely, or secrete resinous and other matters distasteful to the insect in greater quantity and are thus capable of healing the wounds, or in some other way they do not respond to the attack or suit the insect. In any case the attack on the leaf rather than the root seems to be the exception in European vineyards and the rule in American species, and we appear to be face to face with a problem of specific predisposition to this particular malady. That the resistant properties of the vines of America--not all, only particular species and varieties are thus "immune"--can be utilised has been proved by European growers; and not only so, for Millardet and others have shown that the European vine grafted on to these resistant stocks suffer less than when on their own roots. It has also been shown that hybrids can be obtained which are resistant. But the most curious point of all is that _Phylloxera_ was itself a native of America, and came thence to Europe. It had played its part with certain fungi in ruining all the attempts to introduce the European vine into America many years ago. A recent authority on the evolution of American fruits writes as follows: "All the most amenable types of grapes had long since perished in the struggle for existence, and the types which now persist are necessarily those which are, from their very make-up or constitution, almost immune from injury, or are least liable to attack . . . the _Phylloxera_ finds tough rations on the hard, cord-like roots of any of our eastern species of grapes. But an unnaturalised and unsophisticated foreigner, being unused to the enemy and undefended, falls a ready victim; or if the enemy is transported to a foreign country the same thing occurs." Further proof that it is in the "constitution" of the European vine that the want of resistance to _Phylloxera_ resides, is furnished by the fact that in California and the Pacific states the European vine was introduced with more success, but is now suffering badly because _Phylloxera_ has spread there also. It must not be overlooked, however, that we are as yet very ignorant of all that is implied in the word "constitution" as used above.