MEDICAGO FALCATA, A YELLOW-FLOWERED ALFALFA. 25 
other botanists class Medicago falcata as a distinct species coordinate 
with Medicago sativa. | 
While opinions differ as to the relationship of A/edicago sativa to 
Medicago falcata, the natural relationship is clearly indicated by the 
frequency and fertility of the hybrids between the two. With the 
exception of the forms of Medicago which Urban (62) assigns to 
Medicago sativa and Medicago prostrata Jacq. (28) there are no 
others so far reported that hybridize naturally with Medicago 
satwwa—and but few that can be crossed artificially.t 
These facts are especially significant in the Leguminose, where 
hybrids of any kind are extremely rare. A careful study of the 
behavior of the hybrids of Medicago sativa and Medicago falcata 
Fie. 12.—Individual plant of Medicago falcata, S. P. I. No. 28070, a medium broad 
crowned plant of ascending habit of growth, representing Group III. 
points to a common origin of the parents at no very remote date in 
their evolutionary history. Regardless of the somewhat contradic- 
tory opinions that exist, Medicago falcata will be referred to through- 
out this paper as a true species. 
Botanical names have been assigned to what appear to be true 
forms of Medicago falcata and both specific and varietal names 
to forms that are apparently hybrids of Medicago falcata and Medi- 
1 Hybrids of Medicago sativa and Medicago prostrata have been reported by Ascherson 
and Graebner, but there is a much closer relationship between these species than Urban’s 
classification would indicate. Numerous broad crosses of legumes have been reported, 
including one of Medicago sativa and an annual or biennial species of the same genus, but 
they are all of doubtful authenticity. 
55890°—Bull. 428—17 4 
