1. The development of flower buds inSoldanella minima grown at 15° or above is stopped at the stage of sporogenous cells in the anthers. 2. Low temperature overcomes this inhibition, resulting in microsporogenesis and subsequent flowering. Microsporogenesis must thus be considered as a phase initiated only at low temperature. Photoperiod does not seem to playa decisive role in this process. 3. Applied gibberellic acid substitutes for the cold requirement of the flower buds.