588 
Journal of Agricultural Research 
Vol. XXXI, No. 6 
As a result of this first observation seeds of annual and biennial 
white sweet clover were sown in the greenhouse on December 24, 1921, 
and the flats subjected to various periods of illumination: (1) Normal 
day for that time of year, about hours; 9 (2) short day, from 
9 a. m. to 4 p.m.; (3) long day, from daylight to dark, with illumina¬ 
tion, from twilight until lip. m., by three 200-Watt electric lamps 
hung about 2 feet above the flats. The temperature of the green¬ 
house was 50 to 60° F. The rise of temperature caused by the electric 
lights was inconsiderable, as was that in the dark chamber. 10 * Under 
these conditions the following six lots of seed were tested: 
2066. Grundy County biennial, an eaily dwarf form. 
2140. Commercial biennial. 
03464. Arctic biennial, an early dwarf form. 
2143. Mixed annual. 
12055. A late annual selection. 
12060. An early annual selection. 
The seedlings were measured 51 days after sowing. The measurements are 
given in Table II. 
Table II.— Average length of the first internode , average stem length , and average 
internode length of seedlingSj 51 days from sowing on December 24, 1921 
[Measurements in millimeters] 
3-leaved 
4-leaved 
Biennial 
Annual 
Biennial 
Annual 
2066 
2140 
03464 
2143 
12055 
12060 
2066 
2140 
03464 
2143 
12055 
12060 
[r- 
8.5 
12.3 
11.6 
14.4 
19 
16.9 
10.9 
15 
13.9 
14.3 
19.6 
17 
® N-.-iS_ 
14.3 
22.4 
17 
25 
36 
30 
22 
29.3 
26 
33.5 
45.5 
38.1 
U- 
1.9 
3.4 
1.8 
3.5 
5.7 
4.4 
2.8 
3.6 
3 
4.8 
6.5 
5.4 
\v _ 
3 
5 
8.5 
6.2 
6 
5.3 
4.8 
5.5 
8.6 
6.8 
7.1 
5.5 
fi. 
4.45 
7.35 
18.3 
10 
10 
8 
7.6 
9.9 
18.8 
12.5 
11.8 
8.3 
ll- 
.5 
.8 
3.3 
1.3 
1.3 
.9 
.7' 
1.1 
2.5 
1.4 
1.2 
.7 
fl'- 
13.3 
18.8 
23.6 
21 
23.7 
20.4 
15.4 
18.3 
28 
, 23.2 
23.6 
22.2 
L_<S_ 
28 
40 
43.5 
44.3 
45 
40.9 
40.2 
48.5 
57 
58.8 
58 
55.7 
ll- 
4.9 
7.1 
6.6 
7.4 
7.1 
6.6 
6.2 
7.5 
7.2 
8.9 
6.1 
8.4 
«iV= normal day. S=short day. X=long day. J'=length first internode; cotyledons to unifoliolate 
leaf. S=stem length; cotyledons to growing point. 1 =average length all internodes above the first. 
This figure is found by dividing stem length from unifoliolate leaf to growing point by the number of 
trifoliolate leaves. ' 
It will be noted that the first internode is always considerably 
longer than the others. For example, in Table II, if the length of 
the first internode of 2066, biennial, for normal day, is deducted 
from the total stem length, the length above the unifoliolate leaf is 
5.75 millimeters, or an average of slightly less than 2 millimeters per 
internode. In 2143, annual, this length is 3.5 millimeters. In the 
three and four leaved seedlings, the length of the first internode, 
under normal day, equals or exceeds that of the entire stem above 
the unifoliolate leaf, but in older seedlings this relation changes. See 
Table III, where in the normal day columns for the seven-leaved 
seedlings, the average length of each internode above the unifoliolate 
leaf is but little less than that of the first internode. 
o Data from Garner, W. W., Bacon, C. W., and Allard, H. A. photoperiodism in relation to 
HYDROGEN-ION CONCENTRATION OF THE CELL SAP AND THE CARBOHYDRATE CONTENT OF THE PLANT. JOUT. 
Agr. Research 27: 119-156, illus. 1924. 
Oakley, R. A., and Westover, H. L. effect of the length of day on seedlings of alfalfa 
VARIETIES AND THE POSSIBILITY OF UTILIZING THIS AS A PRACTICAL MEANS OF IDENTIFICATION. Jour. 
Agr. Research 21: 599-608, illus 1921. 
