472 KARLING: GROWTH AND REPRODUCTION IN CHARA 
In the mild winter of 1923-24 the plants did not die down 
but remained alive under the ice when the pond was frozen 
over. Healthy green plants were secured throughout the entire 
winter. On several visits to the pond it was frozen over with a 
thin sheet of ice, and when the ice was broken away the plants 
were found to be in a dormant, healthy condition with a deep 
green color. The temperature under the ice was approximately 
2°C, The plants at that time were only about 15 cm. in length, 
including the dead basal end. The internodes were 13 to 15 
mm. in length and .75 mm. in diameter. The leaves and main 
axis were covered with brownish-colored plankton forms. 
The formation of antheridia and oogonia in Chara fragilis, 
according to Migula (25) and Robinson (30), occurs generally 
from July until September. When this bed of Chara was dis- 
covered on September 19, 1923, there were no indications of 
reproductive organs. The plants were examined carefully 
throughout the winter for the appearance of these structures 
The first antheridia and oogonia occurring spontaneously were 
observed on May 26, 1924. The plants were still partly covered 
with brownish plankton, but they had increased several inches 
in length and branched freely. 
EXPERIMENTAL METHODS 
Large masses of plants were brought into the laboratory and 
grown in shallow pots with sand loam as a substratum and 
placed in battery jars. The battery jars were of various sizes, 
ranging from 15 to 30 cm. in diameter and 30 to 45 cm. in depth. 
The taller jars were found to be more favorable than the smaller 
ones. Tap water was used in every case. Very little difficulty 
was encountered from invasion of algae. A small crustacean 
was introduced into the jars to keep down the growth of the algae 
whenever they became abundant. When necessary the pots 
were lifted out and the jars were cleaned. Fresh water was 
added once or twice every month. 
The cultures were placed in north, east, south and west 
windows in the laboratory where they received varying degrees 
of illumination. All cultures with the exception of those in the 
north windows received the direct rays of the sun several hours 
each day. e reponse to this increase in illumination and 
temperature was immediate in every culture. The plants began 
