Luther Burbank of Santa Rosa, California, has produced a great many hybrid brambles, the qualities of which in many respects surpass those of the wild species. Most of them are only propagated by cuttings and layers, not being stable from seed. But some crosses between the blackberry and the raspberry (_R. fruticosus_ and _R. idaeus_) which bear good fruit and have become quite popular, are so fixed in their type as to reproduce their composite characters from seed with as much regularity as the species of _Rubus_ found in nature. Among them are the "Phenomenal" and the [269] "Primus." The latter is a cross between the Californian dewberry and the Siberian raspberry and is certainly to be regarded as a good stable species, artificially produced. Bell Salter crossed the willow-herbs _Epilobium tetragonum_ and _E. montanum_, and secured intermediate hybrids which remained true to their type during four successive generations. Other instances might be given. Many of them are to be found in horticultural and botanical journals which describe their systematic and anatomical details. The question of stability is generally dealt with in an incidental manner, and in many cases it is difficult to reach conclusions from the facts given. Especially disturbing is the circumstance that from a horticultural point of view it is quite sufficient that a new type should repeat itself in some of its offspring to be called stable, and that for this reason absolute constancy is rarely proved. The range of constant hybrids would be larger by far were it not for two facts. The first is the absolute sterility of so many beautiful hybrids, and the second is the common occurrence of retrogressive characters among cultivated plants. To describe the importance of both these groups of facts would take too much [270] time, and therefore it seems best to give some illustrative examples instead.