1070 
Journal of Agricultural Research 
Vol. XXVIII, No. I 1 
at 2 p. m., and in the 10-hour exposure as 5 p. m. Those which were given the 
full day exposure were treated in the same manner as the other plants except 
that they were not darkened. 
In mentioning sex ratios the number of carpellate to 100 staminate plants has 
been used throughout this paper. 
The effects produced by the various lengths of exposure to light are shown by 
the summary which is given in Table I. 
Jan. Feb.Mar. April May June July Aug. Sept.Oct. Nov. Dec. 
Fig. 1.—Graph showing the changes in length of day during the year in the latitude of Boston, Mass. 
Ordinates indicate 2-hour intervals of the day and abscissae indicate monthly periods of the year 
Table I.— Effect of day length on growth and reproduction 
Day length 
Date 
planted 
Budded 
Sex 
ratio 
Total 
number 
Number 
died 
Height 
5 hours_ 
May 13 
_ Ho 
June 21 
128:100 
128 
19 
Meters 
0.21 
7 hours....... 
June 14 
119:100 
101 
20 
0.50 
10 hours.. 
...do. 
June 15 
111:100 
95 
11 
0.75 
Day—inside.—_____ 
_do_ 
Aug. 13 
July 14 
Aug. 14 
115:100 
73 
23 
2.05 
Day—outside..... 
...do. 
140:100 
120 
4 
1.04 
Day—in plat.... 
_do_ 
97:100 
133 
3.38 
Total. 
117:100 
650 
82 
BEHAVIOR OF THE PLANTS 
Five-hour exposure. —Plants which were exposed to light for only 5 hours 
daily showed very little development of either the vegetative or the reproductive 
parts. Side branches were absent and the leaves were few in number, small, 
and yellowish green in color. The number of flowers produced was very small 
and the maximum crop of seed matured by single carpellate plants was not 
over 12. Flower buds first appeared 38 days from the date of planting. The 
