No. 548] 



HARDINESS IN ALFALFA 



407 



201 series. Two of these instances were Turkestan al- 

 falfas. The third one was due to the fact that the 202 

 row was an outer row, thus not afforded protection by 

 an adjacent row. 



In our theoretical discussion of the data we can 

 scarcely more than present the problem. Within the 

 limits of the pure Medicago sativa, as pure as it exists 

 to-day, the fact is patent that there is a wide range of 

 diversity in hardiness among the different strains of 

 alfalfa, dependent in greatest measure upon their geo- 

 graphical origin. Strains of Medicago sativa that have 

 been grown for long periods in cold climates, e. g., Mon- 

 golian alfalfas, are found to be hardy during the severe 

 winters of this country. Upon the other hand the strains 

 of this species which have been grown for long periods in 

 hot countries, e. g., Arabia and Peru, were found to be 

 exceedingly tender in cold districts. Thus at Dickinson, 

 North Dakota, it has never been possible to bring alive 

 through the winter a single plant of the Arabian alfalfas, 

 and only under exceptionally favorable conditions has it 

 been possible to winter any of the Peruvian alfalfa 

 plants. 



The diversity is so great between the Arabian and the 

 Mongolian alfalfas that we must consider that hardiness 

 has actually been added to the alfalfas which have become 

 hardy, or that hardiness has been lost to alfalfas that 

 have become tender. 2 It is not unlikely that changes 

 have been brought about in both directions. The simple 

 problem is, has this change come about through the 

 "law of ancestral inheritance,' 1 or must the change be 

 accounted for by distinct mutations occurring within any 

 particular strain of alfalfa? Or is it possible that 

 changes have come about through conformity to both 

 methods? 



2 The fact is not lost sight of that an increase of hardiness may possibly 

 be brought about by a recombination of certain (at present unknown) 

 morphological characters physically responsible in different ways for the 

 presumably complex character of hardiness. See Nilsson-Ehle, "Kreuzungs- 

 untersuchungen," Lunds Univ. Ars., Bd. 5, Nr. 2, p. 114. Also a forth- 



