KARLING: GROWTH AND REPRODUCTION IN CHARA 473 
to grow vigorously and branch freely. Two cultures of the 
plants and a control were used in each of these preliminary 
experiments. The plants were allowed to acquire a good vege- 
tative development by leaving them in their positions for several 
days to weeks before they were subjected to experimental 
conditions. For increasing the period of illumination a 60-watt 
120-volt mazda lamp was placed approximately 8 cm. above 
the battery jars. In every case the light bulbs were immersed 
in a battery jar of water to prevent an increase in temperature 
when they were burning. In all experiments the light was turned 
on at sunset; and the daylight period was reckoned from sunrise 
to sunset. The intensity of illumination when the sun was not 
shining directly on the cultures was measured rather roughly 
each week with a foot-candle meter. The controls in every case 
were covered with blackened bell-jars at sunset. The electric 
light was used only to supplement the normal daylight of the 
period of each experiment, and was not turned on until sunset. 
At the time that Chara fragilis began to fruit out-of-doors on 
May 26, 1924, the period of daylight had increased more than 
five hours over that in January when the experiments were 
begun, Thus the last cultures studied were receiving relatively 
more daylight and less electric illumination. The increase of 
the daylight period is shown in 
A thermometer was placed in each battery jar, and tempera- 
ture readings were made at intervals of four hours. Each culture 
was examined daily with a hand lens, and when there were 
indications of antheridia and oogonia the plants were examined 
with the low power of a microscope to determine with certainty 
the presence of reproductive organs. Photographs were made 
as soon as the first antheridia and oogonia had reached full size. 
Representative plants from each culture were selected and 
photographed. Records of the cultures are here reported, 
covering the period from October 18, 1923 to November 6, 1924. 
OBSERVATIONS AND RESULTS 
SERIES 0, CULTURES 0-I AND 0-2 
Collected in park pond...... Culture o-1, Oct. 18; Culture 0-2, Dec. 28 
Outside on east window-sill.. 0:0... 2 coe ces es weet 0. c 18 to Jan. It 
Inside on shelf before east window with all-night electric illumination 
n, 11 to March 26 
On shelf in east window with only daylight illumination. . March 26 to Nov. 6 
