NO. 6 EFFECTS OF LIGHT ON ALGAE MEIER 7 



For this experiment, a 300-watt Mazda daylight lamp was placed 

 under each of the four water baths. Under baths i, 2, and 3 the bulb 

 was placed so that the filament was 20 centimeters from the glass 

 bottom of the bath. For bath 4 the distance was 40 centimeters. In 

 bath I the cultures were stationary; the cultures in the other three 

 baths were continuously agitated so that the cells were more evenly 

 dispersed in the culture media. Cultures in baths i, 3, and 4 were 

 lighted continuously throughout the experiment, but those in bath 2 

 were illuminated for 6 hours daily from i a.m. to 7 a.m. 



This experiment was of one month's duration from June 19, 1931, 

 to July 17, 193T. 



RESULTS 



A. As regards grow'uuj cuiulitioiis. — 



1. The best development took place in those cultures grown under 

 natural conditions of light and darkness in a north window of the 

 tower. 



2. Of the cultures grown under artificial conditions in the baths, 

 the best ones were those grown in intermittent light at about a 

 distance of 20 centimeters from the light. 



3. The next best Detmer cultures were those grown in l^ath 4 at a 

 distance of about 40 centimeters from the light. 



4. The cultures in baths i and 3 gave the poorest results. There 

 was continuous illumination at a distance of about 20 centimeters in 

 both of these baths and in one set the cultures were stationary and 

 in the other, continually shaking. 



B. As regards solutions. — 



1. The cultures of Detmer J both with rubber stoppers and cotton 

 plugs showed the best growth and most normal cells under all the 

 different conditions. 



2. All the other cultures showed poor growth under continuous 

 light at 20 centimeters distance from the light in baths i and 3. 



3. The cultures in which the potassium chloride of the Detmer 

 solution was replaced by potassium acid carbonate did not give as 

 good results as the Detmer ^j solution. 



4. The algae in the Johnston solution were a brighter green than 

 the algae in the Detmer solution in the tower cultures. 



5. The most normal algal cells occurred in the Emerson. Johnston, 

 and Detmer solutions in the tower and in intermittent light, bath 2. 



6. The cells of the stationary cultures were irregularly shaped and 

 showed abnormally cut plastids. 



7. The cells in the cultures 20 centimeters from the light, con- 

 tinuously illuminated, were very tiny. 



