July is, 1931 
Effect of Length of Day on Seedlings of Alfalfa 
601 
of the several varieties is well illustrated in Plates 111 and 112. While 
there were some differences between the seedlings of the several varieties 
from May and June sowings, the Kansas and Grimm more nearly ap¬ 
proached those of the Peruvian in height and very closely resembled 
each other. The Grimm seedlings did not take on the branching or 
rosette-like habit of growth so characteristic of seedlings from fall sow¬ 
ings. The spring seedlings of the Grimm were also much more uniform 
than the fall seedlings and closely resembled the Kansas and Peruvian in 
this characteristic. (PI. 113, 114, 115.) 
RELATION OF ALFALFA SEEDLINGS TO PHOTOPERIODISM 
After a study of the behavior of the alfalfa seedlings from sowings 
made at different times of the year and at different latitudes it was 
concluded that the marked differences exhibited by seedlings of the sev¬ 
eral varieties from fall sowings at Arlington and North Ridgeville were 
due chiefly to the effect of cool weather. With no marked varietal 
differences from the May and June sowings, this conclusion seemed 
entirely justified. The significance of the fact that greenhouse tests 
made in December at Washington produced striking differences between 
the varieties was not appreciated by the writers at that time. Later, 
however, the results of Gamer and Allard 1 from their investigations in 
the photoperiodism of plants caused the writers to suspect that the 
length of day might, to some extent, be involved in the phenomenon 
exhibited by the seedlings of the various alfalfas included in their studies. 
Consequently experiments were outlined and undertaken in the green¬ 
house on the Department of Agriculture grounds at Washington. On 
January 20 seed of Peruvian alfalfa, Kansas, Grimm, Turkestan, and a 
strain of Medicago falcata was sown in three flats. One flat was given 
the effect of the normal length of day, one was put in total darkness at 
4 p. m. and left there until 9 a. m., and one had the length of day aug¬ 
mented by an electric light and reflector placed about 2 feet above it. 
The light was turned on a half hour before sundown each day and turned 
off at 11 p. m. The length of both the short and long day was fixed 
at what was regarded as extreme. The former was fixed largely as a 
matter of convenience to suit the working hours of the gardener and the 
latter to insure the effect of a considerably increased period of illumina¬ 
tion. The day-night treatments apparently produced no effect on the 
germination of the seeds, but as is almost invariably the case the M. 
falcata seed germinated more slowly and unevenly than the others. 
The Grimm and Turkestan resembled the M. falcata in a general way in 
these respects. The Peruvian and Kansas seed germinated with about 
the same rapidity and uniformity. The differences, if any, were in 
1 Garner, W. W., and Allard, H. A. eppect op the relative length op day and night and other 
FACTORS OP THE ENVIRONMENT ON GROWTH AND REPRODUCTION IN PLANTS. In JoUT Agr. Research, 
v. 18, no. 11, p. 553-606, 3 fig., pi. 64-79. 1930. Literature cited, p. 605-606. 
