Hayes and Garber - Cucurbit Breeding

216 BREEDING CROP PLANTS
belong to the species Medicago sativa.
The only closely related
species of economic value is M. falcata, sometimes called
sickle alfalfa or yellow-flowered alfalfa. The two species cross
readily, as Waldron (1919) has shown (for pollination studies on
alfalfa see Chapter III. Piper et al (1914) found that alfalfa set
more seed when cross-pollinated than when selfed, although the
selfed set considerable seed. It also was demonstrated that
automatic tripping with consequent self-pollination may occur
under certain conditions.
Grimm Alfalfa and Winter Hardiness. Westgate (1910) and
later Brand (1911) suggest that the origin of Grimm alfalfa is
probably the result of natural crossing between cultivated alfalfa,
M. sativa, and wild plants of the yellow-flowered sickle lucern,
M. falcata, found especially in Germany, Austria, Roumania,
and certain regions of Italy. The seed from which the Grimm
variety eventually resulted was brought to Carver County,
Minnesota, by a German immigrant farmer, Wendelin Grimm,
in 1857. Here for 50 years the original variety was subjected
to the severe Minnesota winters and as a result the non-hardy
types were eliminated. At the present time Grimm alfalfa is
probably the hardiest variety grown.
Waldron (1912) reported the result of testing for winter hardiness
sixty-eight different strains of alfalfa assembled from various
parts of the world. The trial was made at Dickinson, N. Dak.
during the severe winter of 1908-09. The two strains of Grimm
alfalfa included in the experiment proved to be the hardiest.
On an average, less than 5 per cent, of the Grimm plants were
killed and only one other strain showed less than 10 per cent, killed.
Disregarding twelve strains which were destroyed completely, the
average percentage killed for the other strains, considered as a
unit, was 77.5.
To bring out the fact that differences between strains in
their respective reactions to cold are genetic, Waldron computed
FIG. 52. Structure of alfalfa flowers.
1. Branch showing flowers in position.
2. Single flower showing a, standard; b, sexual column in contact with
standard; c, keel; d, wings.
3. Seed pod.
4. Flower parts in position a, undeveloped pod; b, ovary; c, filament; d,
anther.
5. Same with all anthers removed except one to show stigma.
6. Anther.
Size: 1, about %n; 2, about 2n; 3, about ?n; 4, 5, 6, greatly enlarged.