A goodly number of constant hybrids are described in literature, or cultivated in fields and gardens. In such cases the essential question is not whether they are now constant, but whether they have been so from the beginning, or whether they prove to be constant whenever the original cross is repeated. For constant hybrids may also be the issue of incipient splittings, as we shall soon see. Among other examples we may begin with the hybrid alfalfa or hybrid lucerne (_Medicago media_). It often originates spontaneously between the common purple lucerne or alfalfa and its wild ally with yellow flowers and procumbent stems, the _Medicago falcata_. This hybrid is cultivated in some parts of Germany on a large scale, as it is more productive than [265] the ordinary lucerne. It always comes true from seed and may be seen in a wild state in parks and on lawns. It is one of the oldest hybrids with a pure and known lineage. The original cross has been repeated by Urban, who found the hybrid race to be constant from the beginning. Another very notorious constant hybrid race is the _Aegilops speltaeformis_. It has been cultivated in botanic gardens for more than half a century, mostly in annual or biennial generations. It is sufficiently fertile and always comes true. Numerous records have been made of it, since formerly it was believed by Fabre and others to be a spontaneous transition from some wild species of grass to the ordinary wheat, not a cross. Godron, however, showed that it can be produced artificially, and how it has probably sprung into existence wherever it is found wild. The hybrid between _Aegilops ovata_, a small weed, and the common wheat is of itself sterile, producing no good pollen. But it may be fertilized by the pollen of wheat and then gives rise to a secondary hybrid, which is no other than the _Aegilops speltaeformis_. This remained constant in Godron's experiments during a number of generations, and has been constant up to the present time. [266] Constant hybrids have been raised by Millardet between several species of strawberries. He combined the old cultivated forms with newly discovered types from American localities. They ordinarily showed only the characteristics of one of their parents and did not exhibit any new combination of qualities, but they came true to this type in the second and later generations.