RELATION OF ALGAE TO DISSOLVED GASES. 195 
moderate light and temperature (about 20° C.), lived for 
over a month, but died, eventually, without any apparent 
cause. 
In the above table it will be seen that Hydrodictyon in 
oxygen became much brighter than the check or that in COz. 
This was true of all the others in oxygen, though in less 
degree. This fact, though needing further confirmation, 
agrees with that of Senn (’99), obtained with Celastrum. 
He placed cultures of Celastrum reticulatum in culture solu- 
tion (0.2% Knop’s solution) in Erlenmeyer flasks, one set 
being supplied with oxygen and the other with carbon- 
dioxide somewhat as my cultures were. He placed some in 
the dark and some in diffuse light. After six days the flasks 
were opened and investigated. He says: “Schon dem blos- 
sen Auge boten die Sauerstoffculturen einen ganz anderen 
Anblick als diejenigen mit Kohlensiuere. Wahrend man 
bei den letzteren mit Miihe am Boden des Flaschens einen 
griinen Schimmer entdecken konnte, zeigten die Sauerstoff- 
culturen einen deutlichen, prichtig frisch griinen Boden- 
tiberzug. Unter dem Mikroskop stellte es sich nun heraus 
dass die mit Sauerstoff cultivirten Algen zahlreiche einzelne, 
prachtig griine aussehende Zellen gebildet hatten; dieses 
frisch griine Aussehen hatte seinen Grund darin, dass die 
Zellen ihre Stirke véllig verathmet hatten.” 
Still further, and, perhaps, more remarkable, he produced 
bright green chlorophyll in yellow resting cells of the same 
plant in ten days, by means of a culture solution saturated 
with oxygen, while similar cultures supplied with COz, 
instead of oxygen, produced only a reddish-yellow color. 
These cultures, with COz, were placed in the light. Of those 
containing oxygen (four in all) two were placed in the light 
and the other two were left in the dark. Oxygen cultures 
in distilled water remained entirely red, showing that culture 
solution (food) was necessary for the formation of chloro- 
phyll. 
With Celastrum microporum he was less successful, es- 
pecially in cultures exhausted with the air-pump. The 
cultures with oxygen showed at the end of the week almost 
