HABIT OF GROWTH. 87 



their growth from the air. Thus the soil must have 

 air in it or they cannot live. Waterlogged soils are 

 barren of useful bacteria. Thus well drained soils 

 are best for alfalfa. The bacteria thrive in soils 

 alkaline, not acid. They cannot well withstand acid 

 soils. They like a great abundance of carbonate of 

 lime in the soil. It has not been shown that there 

 is ever too much carbonate of lime in the soil for the 

 good of the bacteria. Of other common western 

 alkalies there may be a superabundance some- 

 times of sulphate of soda and other more harmful 

 black alkalies. The alfalfa root is the foundation 

 of the. alfalfa, plant. When it is vigorous the whole 

 plant thrives and resists disease and disaster. 



Resisting Temperature Extremes. The alfalfa 

 plant is hardy against cold. One could almost trace 

 alfalfa to' its original home by its very habit of re- 

 sisting extreme heat and at the same time freezing 

 cold. Desert countries have often blistering days 

 and freezing nights. Alfalfa will be green nearly all 

 winter down next the earth, waiting its chance. As 

 soon as there is sun and warmth of spring 

 it begins its growth. It is hardier than com- 

 mon red clover and earlier to start in spring. 

 Different strains of alfalfa have different de- 

 grees of resistance to cold. Cold affects the 

 alfalfa differently at various stages of growth. 

 When a warm spell in early spring pushes it up to 

 a swift, succulent growth a hard freeze will lay it 

 all over as though it were killed. It may indeed be 

 seriously set back by such a freeze but usually it 



