Formation of Cleistogamic and Chasmogamic Flowers in Wild Violets as a Photoperiodic Response

Abstract

IN the spring of 1938, an investigation was undertaken to study experimentally the physiological conditions for cleistogamy in violets. It seemed obvious that the results of Bergdolt¹ do not offer a satisfactory explanation of the occurrence of this phenomenon in Nature. Nutritional difficulties are not likely to occur suddenly and so regularly as to account for the seasonal appearance of cleistogamic and chasmogamic flowers. As a matter of fact, most of his experiments also indicate an influence of the photoperiod. Curiously enough, Uphof² in his review of cleistogamic flowers overlooked the influence of this ecological factor, although a detailed investigation by Allard³ showed the decisive effect of the photoperiod for the formation of cleistogamic and chasmogamic flowers in the hog peanut (Falcata comosa). Garner and Allard⁴ also report on the influence of day-length actually for a species of violet (Viola fimbriatula).