596 
Journal of Agricultural Research 
Vol. XXXI, No. 6. -* 
are considered. In both two-leaved and three-leaved seedlings the 
plants from the raised bench are shorter than those grown farther 
from the light. In many cases this length is nearly the same as that 
secured under the short day. 
Comparing these two sets with those grown under normal day at 
about 6 feet from the glass, it will be noted that the effect of growing 
the seedlings near the glass has been expressed in the same direction 
and often to the same degree as has that of decreasing the time of 
illumination. Increasing the duration of illumination has again 
resulted in a marked increase in length. 
One trial with Melilotus indica may be mentioned here as an ex¬ 
ample of the striking effect photoperiodicity may exert. Seeds 
of this species were sown November 16, 1922, and the seedlings re¬ 
moved and pressed February 17, 1923. The behavior of those under 
short day was not at all remarkable—indeed they can not be readily 
distinguished from those grown under normal day—but the seedlings 
under long day show striking changes (pi. 6). Not only have the 
internodes been lengthened, but the plants have flowered and fruited 
when only 93 days old and barely 9 to 11 cm. long. Moreover, 
the leaflets are decidedly smaller than those of seedlings grown 
under normal day. This behavior of Melilotus indica under long day 
is quite in harmony with its field behavior. When grown in the 
South, it blooms as soon as the days get longer in spring, and in the 
North it has no value because it runs to bloom when only a few inches 
high. It has been thought that the warm days of a northern May 
accounted for this, but it now seems probable that the long period 
fo sunshine rather than the temperature is the exciting cause. 
CONCLUSION 
It has been shown that the internodes of the annual white sweet 
clover are longer than those of the biennial. This is most marked 
in seedlings grown out of doors in late summer and is then sufficient 
in degree to serve to distinguish the two. Under a short or a long 
day in the greenhouse the differences tend to disappear, and con¬ 
trolling the period of illumination can not be recommended as a 
useful method in this case, though Oakley and Westover found it 
useful in alfalfa varieties. 
o 
