3838 BULLETIN 428, U. S. DEPARTMENT OF AGRICULTURE. 
PERIODS OF GROWTH. 
Observations made at Brookings in 1912, 1913, and 1914 indicate 
that Medicago falcata has a tendency to commence growth earlier in 
the spring than Medicago sativa or Medicago satwa X falcata 
hybrids. This characteristic is apparently influenced by climatic and 
soil conditions. If, as frequently happens in early spring, a short 
period favorable for growth is followed by continued cool or cold 
weather, the difference between the quantity of growth of Medicago 
falcata and Medicago sativa when the growing season really begins is 
very noticeable. This probably is due to the fact that while both may 
Fic. 17.—Loose bunches of stems of various forms of Medicago falcata, showing general 
types of growth. 
start during the favorable period, the former is able to outgrow the 
latter during the unfavorable period following. 
At Highmore, 8. Dak., in the spring of 1912, M/edicago falcata con- 
tinued growth throughout an extended period of very cold weather, 
while J/edicago sativa made very little growth. The same phenome- 
non was observed at Brookings, but the difference between the two 
was not so pronounced. In the spring of 1914 the difference in the 
earliness of growth was less noticeable than in the other seasons men- 
tioned. The soil was extremely dry until well into April that year, 
after which the conditions of warmth and moisture were unusually 
favorable, resulting in good growth of all varieties. It seems reason- 
able that the lack of difference between the spring growth of Medi- 
