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 
