476 KARLING: GROWTH AND REPRODUCTION IN CHARA 
Culture 0-3 continued to fruit until July. By September 12 
the plants had increased fully 24 cm. in length, were healthy 
and deep green in color. No antheridia and oogonia were present 
on this new growth, however. At the end of October the plants 
had died, but a new growth was beginning at the base of the 
old plants. No reproductive organs have been observed on this 
culture since June 28. The control grew slowly but did not 
fruit during the spring and summer. 
SERIES A 
Collected from under the ice in the park pond I 
Grown on east window-sill in laboratory.................. March 15-19 
In east window under electric light daily from sunset to 1 a. m 
March 1g—April 22 
Grown In north window with only daylight illumination..May 4-Nov. 6 
This culture consisted of three jars of plants brought indoors 
on March 15, at a time when the pond in the park was frozen 
over. As soon as the cultures were placed in the east window 
in the laboratory they began to grow. On March 19 two jars 
were placed under electric light, which was kept burning until 
1a.m. The vegetative growth was more rapid than in the third 
jar, the control. On March 30, eleven days later, antheridia 
and oogonia appeared in abundance in the two jars which had 
been under the electric light, while there was no indication of 
fruiting in the control. On April 22 the experiment was ter- 
minated. Photographs of typical plants made on April 13 are 
shown in Fic. 3, PLATE 11. 
The temperature at which this culture was grown was 15° to 
35° C., as shown in Cuart 1. In some periods the daily range 
was as much as eighteen degrees. This wide daily variation in 
temperature may have been in part the cause of the abortion of 
the oogonia and the subsequent etiolation of the plants. As 
the experiment continued, the plants became light green in color, 
and by the end of April the basal nodes, internodes and leaves 
were almost white in color. 
Owing to the advancing season this culture was receiving 
almost two hours additional daylight above that of the preceding 
one. On March 19 when this experiment was begun the day- 
light period was approximately 12 hours. When the fruiting 
was first observed on March 30, it had increased to 12% hours, 
