Abstract
Since GARNER and ALLARD in 1920 found the three categories of plants, i, e. short-day plants, long-day plants and ever-flowering plants according to the relation between the flowering and the day-length, many plants have been studied to be classified among these three types. It may, however, be considered that there are two different stages in the course of flower formation, namely the differentiation of flower bud and the subsequent development of differentiated bud to flowering, and that these stages would receive the effects of day-length independently. To make clear this relationship some experiments have been carried out by the author during these six years from 1931 to 1936, using sixteen kinds of plants.
