216 BREEDING CROP PLANTS 



belong to the species Medicago saliva. 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. saliva, 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 hardi- 

 ness 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; 6, sexual column in contact with 

 standard; c, keel; d t 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. 



