EFFECT OF THE LENGTH OF DAY ON SEEDLINGS OF 
ALFALFA VARIETIES AND THE POSSIBILITY OF 
UTILIZING THIS AS A PRACTICAL MEANS OF IDEN¬ 
TIFICATION 
By R. A. OaklKy, Agronomist, and H. L. WESTOvER, Agronomist, Forage Crop 
Investigations, Bureau of Plant Industry, United States Department of Agriculture 
At Arlington Farm, Va., a few years ago the writers noted striking 
differences in the habits of growth of young seedlings of the commercial 
varieties of alfalfa produced from seed sown in the early fall. The 
differences in height and general appearance were so great that even a 
casual observer could easily distinguish certain of the varieties. Not 
having noted previously such a marked varietal difference in seedlings, 
the writers were led to the tentative conclusion that the time of sowing 
was, in some measure at least, responsible for the phenomenon. To test 
the validity of this conclusion, experiments were conducted the following 
year in which Peruvian , 1 Kansas , 2 Canadian variegated, Grimm, and a 
yellow-flowered alfalfa (Medicago falcata L.) were sown at Arlington Farm 
in the early fall. The same striking differences that had previously 
been observed were noted. However, May and June sowings at Arlington 
and also at North Ridgeville, Ohio , 3 showed no such marked varietal 
characteristics. This, in a measure, confirmed the conclusions the 
writers had reached and suggested further investigations, which were 
subsequently conducted. 
POSSIBILITY OF DISTINGUISHING VARIETIES OF ALFALFA IN THE 
SEEDLING STAGE 4 
In addition to studying the effect on alfalfa seedlings of sowings made 
at different times of the year, it occurred to the writers that it might be 
possible in this connection to develop a practical method of identifying 
various alfalfas in a relatively short time after samples of seed are avail¬ 
able. Such a method would be useful, indeed, especially in identifying 
the Grimm and Peruvian varieties. In fact, it was chiefly to find a 
means of identifying alfalfas quickly that detailed studies of seedlings 
were undertaken. 
Partly because of availability of location and partly for the purpose 
of testing the effect of latitude on the growth of alfalfa seedlings, 
1 All references to Peruvian alfalfa in this publication are to the hairy strain. 
* For the sake of convenience the term Kansas alfalfa refers to the regional strain of common alfalfa pro¬ 
duced in Kansas. 
* Experiments conducted cooperatively with the Ohio Agricultural Experiment Station at North Ridge¬ 
ville, Ohio, about 3 miles north of Elyria. 
4 Eor the sake of convenience the term variety is used in its broad sense to mean regional strains as well 
as distinct horticultural varieties. 
Journal of Agricultural Research, 
Washington, D. C. 
yr 
(599) 
Vol. XXI, No. 8 
July 15, 1921 
Key No. G-239 
