MEDICAGO FALCATA, A YELLOW-FLOWERED ALFALFA. 39 



cago fdlcata and Medicago sativa in this instance may have been due 

 to these conditions, particularly to the dryness of the soil. 



The various forms of Medicago falcata exhibit slight differences in 

 the earliness of spring growth. It seems to be true that young plants 

 of all alfalfas start growth earlier than old plants. Therefore, only 

 plants of the same age should be compared in making observations on 

 this point. 



In his discussion of Peruvian alfalfa, which he describes as Medi- 

 cago sativa variety polia^ Brand {IB) calls attention to the ability 

 of this strain to continue growth during the late fall and winter 

 when other varieties of Medicago sativa become dormant on account 

 of the low temperature. The term " zero point " is applied by him 

 to the minimum temperature at which growth can be made. He 

 consequently classes Peruvian alfalfa as a variety which has a low 

 zero point and common alfalfa as a variety with a comparatively 

 high zero point. Brand's observations were made in southern Ari- 

 zona, and had Medicago falcata been studied in comparison with the 

 varieties of Medicago sativa it doubtless would have been considered 

 as having the highest zero point of all, since it discontinues growth 

 in the Southwest earlier than any of the other varieties of alfalfa, 



A study of the various alfalfas at different latitudes with regard 

 to their phenological characteristics reveals some rather interesting 

 and important points. The most important of all, perhaps, is the 

 effect of severely low temperatures on their so-called zero points of 

 growth. This can be explained best by citing the behavior of the 

 distinct forms in different parts of the country. In California and 

 the far Southwest, McKee finds it readily possible to distinguish 

 Peruvian alfalfa, common alfalfa, Medicago sativa X falcata hybrids 

 (the general group of variegated alfalfas), and Medicago falcata by 

 their groAvth in late fall and early spring, without regard to their 

 morphological characters. They discontinue growth in the fall and 

 resume it in the spring in the order in which they are named above. 

 The same order obtains in general at the Arlington Farm, Va., with 

 some seasonal variation, but at Brookings and Ilighmore there is a 

 tendency toward the reversal of this order. The latitude of Wash- 

 ington, D. C, appears to be about the dividing line, if high altitudes 

 are excepted. 



SPBING CiROWTH. 



Westgate {00) in discussing Medicago falcata X satina hybrids 

 says, " in earliness of starting in spring as well as in earliness in 

 blooming, the variegated alfalfas appear to exceed the ordinary 

 kinds.'' He f|iialifies this stiitcincut soiiicwhat 1)y saying "In the 

 southern one-half of the United States the variegated alfalfas are 



