But whereas the
hybrid of muricata and biennis is a stout plant, this type is weak with
badly developed foliage, and very long strict spikes. Perhaps it was not
able to withstand the bad weather of the last few years.
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_.
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