APPARATUS FOR CHANGING TEMPERATURE OF A CHAMBER 43 
without it. The writer's record book shows a total of 74 experiments 
performed in February and March, 19 19. Seven of these were of at least 
48 hours duration, about half of the remainder 12 hours, and none less than 
6 hours. Most of the time one short experiment was carried on during 
the day, and one of twelve or more hours' duration was run during the 
night. Out of the total, seven were discarded because the final temperature 
was more than 0.25° C. from that desired. 
Department of Horticulture, 
University of Wisconsin 
