40 BULLETIN 428, U. S. DEPARTMENT OF AGEICULTUEE. 



normally later in starting than the ordinary variety." This indi- 

 cates possibilities worth considering in the development of neAv agro- 

 nomic strains of alfalfa through the hybridization of Medicago sativa 

 and Medicago falcata. It seems quite probable that severely low 

 temperatures materially influence the ability of varieties to commence 

 growth in the spring. In the colder and drier portions of the Great 

 Plains area a variety of alfalfa making a growth in the early spring 

 is more certain of producing a good crop of hay than those that are 

 slow in starting, as it is able to take advantage of the winter moisture. 

 Since one good cutting is sometimes all that can be obtained, the 

 ability of a variety to produce early spring growth is of consider- 

 able importance. Medicago falcata not only possesses this charac- 

 teristic, but is able to transmit it in some degree to the progeny re- 

 sulting from its hybridization with Medicago sativa. 



In May, 1915, the effects of the five severe frosts and freezes which 

 occurred during that month were observed on the nursery rows at 

 Redfielcl, S. Dak. The rows of Medicago falcata showed decidedly 

 less damage than the adjoining rows of Medicago sativa. It is true 

 that the plants of the former, being of lower growth than those of the 

 latter, may have received some protection from the earth. With the 

 exception of the introductions from India, S. P. I. Nos. 26927, 29139, 

 and 30433, the Medicago falcata plants showed almost no frost effect, 

 while those of Medicago sativa were badly wilted. The effect of the 

 frost was apparently the same on the Grimm, Canadian variegated, 

 Baltic, Turkestan, and local Dakota strains. 



EECOVEEY AFTEE CUTTING. 



A characteristic wherein Medicago falcata differs materially from 

 Medicago sativa is in rate of growth after cutting. The ability to 

 produce several crops of hay in a season under faA'orable conditions 

 has been largely responsible for the popularity which the latter has 

 had for centuries. Unfortunately, the former does not possess this 

 ability to any considerable degree; in fact, only under very favor- 

 able conditions can more than one good cutting be procured from it. 



Table II indicates the comparative rate of recovery of Medicago 

 falcata and Medicago sativa after cutting at Brookings. 



Table II. — Comparative rate of recovery of Medicago falcata and Medicago 

 sativa after cutting, at Brookings, 8. Dak., in 1913. 



Plants cut June 19. 



Height of growth — 



Julys. 



July 22. 



Medicago falcata, seven introductions. 

 Medicago sativa, two strains 



Inches. 



4 to 9 



16 



Inches. 

 8 to 13 

 19to20 



