Abstract
Summary Prolonged irradiation with red light and addition of sucrose to the basal medium induced two-dimensional growth in gametophytes of Pteris vittata. The results suggest that two-dimensional growth is controlled by the following three factors: 1. a photoreactive system which depends on blue light; 2. a photoreactive system which can utilize red light; and 3. the photosynthetic system which the level of carbohydrate. Media containing 2.4-dichlorophenoxyacetic acid and sucrose, and complex media containing peptone caused formation of tumor-like calli.