DORMANCY AND GERMINATION IN SEEDS OF ECHINOCYSTIS LOBATA

Abstract

IN THE extensive literature on dormancy in seeds which has appeared during the last twenty-five years, no exact study of this condition in Echinocystis lobata seems to have been reported. Rose (1915) included cucumber in a list of seeds which need after-ripening but gave no suggestion as to how this process may best be brought about. Sempers (1918) reported the inducement of germination by clipping the seed coats or by freezing. This latter method was suggested to him by finding seeds germinating in December in a sand pile of the previous year with which the seeds had been thrown out. Full growth of these plants followed in the spring. Charles (1919) reported successful germination in the spring following fall planting, a practice now recommended by certain seed dealers in their catalogues. She also reported an instance where seeds which had lain on a cement floor under a shed for a year germinated without further planting. This lack of attention to seed germination of Echinocystis has been due probably to the fact that the plant has no economic use and is of little horticultural value. It is, however, a useful plant for teaching purposes. Its rapid growth makes it excellent material for studies in growth rates, while its tendrils provide exceptionally good opportunities for studies in thigmotropic responses. Its use has been greatly limited, however, by the inability to grow plants from seeds stored under ordinary laboratory conditions when needed. It has, therefore, seemed worth while to make a somewhat careful study of the factors involved in the dormancy and after-ripening of these seeds, both from the point of view of securing good material for teaching purposes and for the sake of extending our knowledge of dormant seeds in general. MATERIAL AND METHODS.-Echinocystis lobata (Michaux.) T. and G., Wild Balsam Apple, Wild Cucumber, is native in the northeastern and central United States and has been introduced into the far West. It is sometimes grown as a cultivated plant. The seeds are produced in the fall and may be shed at the time of the bursting of the turgid fruit or mav remain within the capsule until both are fully dry. Material for this study was obtained from several sources, primarily from wild material collected during successive years at Essex, Massachusetts, and from plants grown in the Botanical Garden, Smith College, Northampton, Massachusetts. No significant differences were observed in the results obtained from these two sets of material. During the latter part of the study, material obtained from Bodger Seeds, Ltd., El Monte, California, and from H. A. Dreer, Philadelphia, Pennsylvania, was used. Interesting, though possibly not important, differ-