Abstract
1. Six varieties of tobacco plants were cultured under controlled thermal and photoperiodic conditions, and their developmental responces were compared. 2. The responces of most varieties without "Okinawa" were accerelated in short day (8 hrs.) especially under 18°C, but varietal differences were shown obviously both with degrees and states of their responces. 3. It is necessary to perform further studies to recognize those facts that no responce was shown with "Okinawa" under every condition and "Xanthi" having been classified as day-neutral tobacco showed remarkable acceleration of their development with short day treatment.
