Many instances of so-called atavism are of purely morphologic nature. The most interesting cases are those furnished by the forms which some plants bear only while young, and which evidently connect them with allied species, in which the same features may be seen in the adult state. Some species of the genus _Acacia_ bear bipinnate leaves, while others have no leaves at all, but bear broadened and flattened petioles instead. The second type is presumed to be descended from the first by the loss of the leaflets and the modification of the stalks into flat and simple phyllodes. But many of them are liable to recall this primitive form [177] when very young, in the first two or three, or sometimes in eight or ten primary leaves. These leaves are small because of the weakness of the young plant and therefore often more or less reduced in structure. But they are usually strictly bipinnate and thereby give testimony as to their descent from species which bear such leaves throughout their life. Other similar cases could be given, but this will suffice. They once more show how necessary it is to separate the different cases, thrown together until now, under this general name of atavism. It would be far better to give them all special names, and as long as these are not available we must be cautious not to be misguided by the name, and especially not to confuse different phenomena with one another, because at the present time they bear the same names. Taking into consideration the relatively numerous restrictions resulting from this discussion, we will now make a hasty survey of some of the more notable and generally acknowledged cases of atavism by bud-propagation. But it should be repeated once more that most of the highly cultivated plants, grown as vegetables, or for their fruit or flowers, have so many crosses in their ancestry, that it seems better to exclude them from all considerations, in which purity of [178] descent is a requisite. By so doing, we exclude most of the facts which were until now generally relied upon. For the roses, the hyacinths, the tulips, the chrysanthemums always have furnished the largest contributions to the demonstrations of bud-variation. But they have been crossed so often, that doubt as to the purity of the descent of any single form may recur, and may destroy the usefulness of their many recorded cases of bud-variation for the demonstration of real atavism. The same assertion holds good in many other cases, as with _Azalea_ and _Camellia_. And the striped varieties of these genera belong to the group of ever-sporting forms, and therefore will be considered later on. So it is with carnations and pinks, which occasionally vary by layering, and of which some kinds are so uncertain in character that they are called by floriculturists "catch-flowers." On the other hand there is a larger group of cases of reversion by buds, which is probably not of