Gametophytes of the fern Anemia phyllitidis respond to seven different gibberellins (A(1), A(3); A(4), A(5), A(7), A(8), and A(9)) by forming antheridia. Gibberellin A(7) is active at concentrations as low as 5 X 10(-10) g/ ml. Species from two of the three other genera in the family Schizaeaceae respond similarly to gibberellin A(3). In contrast, nearly 40 species from 7 other families of ferns do not develop antheridia when supplied with gibberellin.

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Abstract.-Light-induced germination of Anemia spores can be inhibited by AMO-1618, a selective inhibitor of gibberellin biosynthesis. The inhibitor has no effect on gibberellin-induced dark germination and its inhibition of lightinduced germination can be reversed by supplying gibberellin. Barley-endosperm bioassay of concentrates of medium in which spores are imbibed in light reveals the presence of substances with gibberellin-like activity; assay of medium from dark-imbibed spores does not. Simultaneous exposure of spores to suboptimal levels of light and gibberellin leads to additivity of effect on germination level. Uptake of labeled gibberellin by spores in light is similar to that in darkness. The implications of these findings for the light-dependent synthesis of a gibberellin-like germination substance are discussed. The bearing of the observations upon understanding the interaction of light and gibberellins in seeds of higher plants is considered.Diverse developmental processes in plants are sensitive to the effects of light and gibberellins. Both the processes of seed germination and of flowering, for example, are stimulated by light exposure and by gibberellin treatment in a wide variety of flowering plants. Spores of various species of ferns have also been shown to germinate in response to red light and to gibberellin.1-5 Most of those species which form antheridia in response to antheridogen-A or -B also dark germinate in response to the same hormone. Both responses occur with species specificity to one of these two antheridogen8, but not to the other antheridogen, showing a striking phyletic parallel between the patterns of activity of the two antheridogens in these very different physiological events.6 For several reasons, the fern spore constitutes a particularly favorable material with which to examine the relationships between light and gibberellin action. In contrast, for example, to the complex multicellular tissues of seeds, the spore is a single cell. In seeds, responses to light and hormones may occur in different cells or tissues; in spores both responses necessarily occur within one cell. Inasmuch as many of the physiological aspects of germination are common to both seeds and fern spores, spores provide a potentially significant and simple model for the more complex processes regulating germination of seeds. The studies reported below are based on the observations that the spores of Anemia phyllitidis do not germinate in the dark and that gibberellin,5 antheridogen-B,6'7 and light each can initiate germination of imbibed Anemia spores. A variety of observations led to a series of experiments designed to test the hypothesis that a germination substance, related to the gibberellins or antheridogens, is synthesized within the illuminated imbibed spore.Materials and Methods.-Source of fern spores: Spore-producing plants of Anemia phyllitidis (L.) Swartz were grown in the greenhouses of the Rockefeller University. Spores were collected, sieved, and stored at 40 until use.8 835

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