ALFALFA 307 



into Greece from Media. Purple medick is ordinary 

 alfalfa, while yellow medick is sickle alfalfa, but the names 

 are rarely used. Black medick, however, is still often 

 used for Medicago lupulina, but yellow trefoil is a more 

 popular name. Erba medica is still an appellation of 

 alfalfa in Italy and the Spanish sometimes use mielga or 

 melga, perhaps corrupted forms of Medica. 



371. Heat relations. In climates of low humidity, 

 alfalfa seems able to withstand extreme summer tempera- 

 tures under irrigation. No injury from heat has ever 

 been recorded in such climates as those of Arizona and 

 Punjab, India. It seems probable, therefore, that the 

 crop is not adapt atively limited in its heat relations. 



High temperatures combined with even moderate 

 humidity are so injurious that the crop is nowhere success- 

 fully grown in humid subtropical or tropical regions. 

 This is partly due to the fact that such conditions are 

 favorable to many weedy plants which smother out the 

 alfalfa, but even if grown in cultivated rows, alfalfa 

 languishes under such climatic conditions. 



372. Cold relations. The minimum temperature that 

 alfalfa will withstand without injury is difficult to deter- 

 mine accurately, as it is affected by other factors, among 

 them variety, degree of dormancy, thickness of stand, 

 soil moisture and snow cover. These factors are further 

 discussed under winterkilling. In Europe, according to 

 Stebler, a temperature of - 13 Fahrenheit is injurious 

 only when the plants are unprotected by snow. 



Brand and Waldron report the effects of winter cold 

 on 68 varieties and strains of alfalfa at Dickinson, North 

 Dakota, in the winter of 1908-1909, when a minimum of 

 31 Fahrenheit was reached. The seeds were planted 

 both in drilled rows and in hills in the spring of 1908, 



