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Gametophyte morphology and development of three species of Cyrtogonellum Ching (Dryopteridaceae) were described with the aim to increase our knowledge on the gametophytic stage of this fern genus especially the occurrence of sexual structures. Spore germination followed the Vittaria-type development, whereas prothallus growth followed the Aspidium-type development. Unicellular glandular hairs were located on both margins and surface of the prothalli. The heart-shaped prothalli of C. caducum showed irregularly lobed margins with multicellular filamentous to wing-like extensions. One to several agamously formed embryos were found on a single mature gametophyte of C. inaequale but only one of these developed into a mature sporophyte. Young sporophytes possessed scales with one to several glandular cells. Antheridia were found in all three species, but archegonia were observed only on mature prothalli of C. fraxinellum, which were always located near the midrib of the cordate-thalloid prothallus. The...

The goal of this study was to determine the function of cytokinin in the morphological development and gender expression of gametophytes of Osmunda regalis, a member of Osmundales, sister-group to all other extant leptoporangiate fern families. Gametophytes of Osmunda regalis were grown in multispore populations on C-fern nutrient enriched agar containing 0, 1 nM, 1 µM, and 1 mM kinetin. Higher concentrations of exogenous kinetin reduced gametophyte size (area), disrupted correlations observed in the control between rates of apical notch formation and thallus widening, increased the proportions of asexuals and males, decreased the proportion of females in the population, and correspondingly increased male reproductive effort (antheridia per unit thallus area) and decreased female reproductive effort (archegonia per unit thallus area) compared to the control. Low concentrations of exogenous kinetin increased the proportion of females compared to the control. In the control, thalli with a comparati...

The spores of Ophioglossum pendulum ssp. falcatum germinated after six weeks in the dark on a nutrient medium containing inorganic nutrients and glucose. The gametophytes grew on the same nutrient medium to give globular, teardrop-shaped, and finally cylindrical gametophytes. The mature gametophytes were cylindrical and highly branched. Other aspects of these gametophytes were normal for Ophioglossum gametophytes with sunken antheridia and short-necked archegonia. The gametangia were functional because fertilization took place in older cultures. Mature gametophytes of O. pendulum ssp. falcatum from culture had the same structure as those of O. pendulum ssp. pendulum from nature. The differing conditions under which the gametophytes of both subspecies grew did not alter their stellate form.

The gametophytic generation of Polystichum pycnolepis (Dryopteridaceae), including spore germination, morphological development of the gametophytes, major vegetative features and sexual expression, was studied. Spore germination was of the Vittaria model and the developmental pattern was of the Aspidium model. Adult gametophytes were cordate and hairy, with unicellular hairs located in the margins and the surface of the prothalli. In addition, hairs of P. pycnolepis were papillate, secretory and the marginal ones septate. Gametangia were of the normal type described for leptosporangiate ferns. The gametophytes produced at first instance a high proportion of female gametophytes. Polystichum pycnolepis formed few bisexual gametophytes with scarce antheridia. No male gametophytes for this species were detected. Thus, the species seemed to be promoting intragametophytic selfing and, to a lesser extend, intergametophytic unions between bisexuals and females.

Gametophyte morphology and development of seven species of Cyatheacae in China are described. The spores of the seven species are of typical shape (trilete, tetrahedral) and they exhibit Cyathea-type germination. The gametophytes undergo Adiantum-type development with occasional Drynaria-type development. Filaments are usually 2-3 cells long. The normal adult prothalli are cordate and thalloid with prominent cushions in the middle of the two wings. Prothalli are usually bisexual and antheridia form earlier than archegonia. Lingulate, strap-like and branched prothalli easily grow on the crowded improved Knop's agar media, which produce notches late and produce more antheridia. In distilled water, filamentous prothalli only produce antheridia. The shapes of the mature prothalli of Sphaeropteris brunoniana and Alsophila austroyunnanensis are distinct among seven species. Multicellular chlorophyllous hairs appear on dorsal or ventral surfaces in the archegonial region near the notch when the prothallus matures, and the hairs are scaly when they get old. Hairs of the prothallus are like those on the juvenile sporophyte fronds. Vegetative proliferations of old protahlli have been observed.

The spores of Lycopodium deuterodensum germinate after 3 weeks in the dark on a nutrient medium containing inorganic nutrients and glucose. The dark grown prothalli have the characteristics associated with Type I and II gametophytes – a ring meristem, radial symmetry, and lack paraphyses and photosynthetic lobes. The younger gametophytes have the carrot shape of a Type II gametophyte with a tapering base, a constricted neck, and a gametangial cap with antheridia. With additional growth, the gametophytes become as wide as long and finally wider than long. The wider than long gametophytes are the first to have both antheridia and archegonia on their gametangial caps. The largest gametophytes grown in culture are Type I with irregular disk shapes. The antheridia on all gametophytes are sunken and, for the Lycopodiaceae, the archegonia have medium sized necks with only 3–4 neck canal cells. Although the specific type of gametophyte has not been determined for this species, those grown in culture have...

Pheromonal interactions between cordate gametophytes of the lady fern, A. filix-femina, were assayed using a protocol typically used for detecting water-soluble pheromones such as antheridiogen. Three week-old, cordate gametophytes were transferred from multispore cultures grown on nutrient agar to agar containing extracts from a previous generation of gametophytes (treatment) and to fresh nutrient agar (control). Three weeks after transfer, fifty gametophytes were examined from treatment and control plates. Each gametophyte was measured for size (area) and shape (circularity) and scored for number of antheridia and archegonia. Treatment gametophytes were significantly smaller, less circular, had fewer archegonia, and possessed antheridia more often than control gametophytes, a pattern consistent with known antheridiogen effects on gametophytes of transitional morphology and sensitivity. The experiment was repeated using gametophytes that were six weeks old at time of transfer to treatment and co...

The spores of Diphasiastrum sitchense germinate in the dark on a nutrient medium containing inorganic nutrients and glucose. Dark-grown prothalli develop into white, carrot-shaped gametophytes with a tapering base, constricted neck, and gametangial cap. The antheridia are large and sunken, and the archegonia have long necks with numerous neck canal cells. The tapering base has a zone of radially elongated cells that is comparable to the inner mycorrhizal zone of Diphasiastrum gametophytes from nature. Although possessing few derived sporophytic characters, D. sitchense has a typical carrot-shaped, Diphasiastrum gametophyte.

Sphaeropteris lepifera is one of the largest tree ferns in Taiwan. On average, it produces 50.7 sporangia per sorus, and 64 spores per sporangium. Spore germination, after 2 years of storage at 4?C was over 95%. The pattern of spore germination was "Cyathea-type", and the gametophytes exhibited mainly Drynaria-type development with occasional Adiantum-type development. Typical gametophytes were heart-shaped but had the potential to elongate and become elliptical. Multicellular hairs on the dorsal and ventral surfaces of the midrib cushion increased in size and changed shape with age. They were usually uniseriate when young, and became multiseriate with age. Gametophytes initiated antheridia about 1 month after spores were sown, and did not become hermaphrodites until 7 weeks later. During ontogeny, the gametangial sequence was from the male to hermaphroditic. Antheridia formed on the wings of the ventral and dorsal surfaces of gametophytes. The wall of each antheridium was composed of 5 cells. Archegonia appeared on the cushion of the ventral surface of gametophytes. Some gametophytes initiated clone-formation through vegetative regeneration. When sufficient water was provided, young sporophytes began to appear 12 weeks after spores were sown. The first fronds were midribless. The uniseriate, multicellular hairs on young sporophytes were similar to those on gametophytes. Gametophyte morphology, including mature forms, spore germination, and types of early development, trichomes, and gametangia, have been used to characterize fern taxa (Stokey, 1918, 1930; Atkinson and Stokey, 1964; Nayar and Kaur, 1971; Atkinson, 1973). These characteristics provide information relevant to fern phylogeny (e.g., Nayar and Kaur, 1971) and the ecology and reproductive biology of different species (Chiou and Farrar, 1997a, b; Chiou et al., 1998; Masuyama, 1975a, b, 1979). In the Cyatheaceae, spore germination is Cyathea-type and gametophyte development is Adiantum-type or nearly Drynaria-type (Nayar and Kaur, 1971). Gametophytes are long-lived (2-6 years) and tend to elongate slightly with age. The multicellular, bristle-like hairs that appear on gametophytes in this family indicate the Cyathaceae is phylogenetically close to the Loxsomaceae (Atkinson and Stokey, 1964). Antheridia and archegonia typically occur on the same gametophytes, with some vigorous gametophytes being strictly archegonial (Stokey, 1930). Apogamy was reported in some species in the Cyatheaceae 1 Corresponding author. This content downloaded from 157.55.39.231 on Wed, 05 Oct 2016 04:13:14 UTC All use subject to http://about.jstor.org/terms AMERICAN FERN JOURNAL: VOLUME 90 NUMBER 4 (2000) TABLE 1. Spore sources, usage, culture medium and storage period.

Gametophyte development was studied in Thelypteris ovata var. lindheimeri from spore germination to 48 days. Spores were sown aseptically onto the surface of agar-solidified mineral medium in multispore cultures. Germination began four days after spore sowing. Game- tophytes were spatulate in morphology at six days and terminal meristems were initiated at ten days. Antheridia were observed at 19 days, archegonia at 21 days. At 28 days, gametophytes were antheridiate (smaller, 0.6-1.0 mm in width), archegoniate (larger, 1.3-2.3 mm in width) or asexual (variable, 0.5-1.5 mm in width). Gametophytes remained unisexual at 48 days. The presence of an antheridiogen system was investigated using culture media extracts of T ovata gametophytes. Young gametophytes of T. ovata and Onoclea sensibilis L. form antheridia prematurely when exposed to partially purified culture media extracts. Two bands of biological activity were present after thin-layer chromatography, indicating the presence of at least two biologically active com- pounds. Studies of gametophyte growth and development play an important role in identifying new species of ferns with antheridiogen systems. Antheridiogens influence growth and development of gametophytes and their sexual mor- phology. They are synthesized by fern gametophytes and cause premature an- theridia formation in developing gametophytes. Antheridiogen systems have been described in several genera of ferns, including Anemia, Ceratopteris, Ly- godium, Onoclea, and Pteridium (reviews by Naf et al., 1975; Raghavan, 1989). In the schizaeaceous ferns, Anemia and Lygodium, antheridiogens also can substitute for the light requirement for spore germination. Morphological char- acteristics of fern gametophytes have been suggested to be of value in the classification of some fern groups (Stokey, 1951; Atkinson and Stokey, 1964). These morphological characteristics are obtained by studies involving growth and development of fern gametophytes from spore germination to reproductive maturity. Unfortunately, these studies are few considering the number of fern

could control the sex expression of fern gametophytes was made in the laboratory. In 1950, Dopp published a paper in which he showed that old media or aquatic extractions from media containing female gametophytes of bracken (Pteridium aquilinum) induced antheridia formation in young gametophytes of its own species or those of the male fern (Dryopteris filix-mas). This pioneer work was supplemented by two further publications in 1959 and 1962. In the United States, it was mainly Naf (for review see Nif, 1979) who started studies on antheridiogen in the late 1950's. Some of the most interesting questions that arose were: Does a selected fern taxon produce or react to antheridiogen? Are antheridiogen-systems widely distributed? What is the sex expression of isolated gametophytes? How much antheridiogen is required to induce antheridia? What happens to a culture of young sterile gametophytes when antheridiogen of a female or a meristic gametophyte is added? Do meristic gametophytes become insensitive to antheridiogen? Since D6pp's initial work, a large number of publications have appeared. Nearly all of these have been based on laboratory investigations and our knowledge of antheridiogen has increased strikingly. It has been shown that at least three main classes of antheridiogens occur (Nif, 1979), antheridiogen A (bracken-antheridiogen), antheridiogen B (produced by members of the family Schizaeaceae) and antheridiogen C (produced by species of the genus Ceratopteris). Although the chemistry of only antheridiogen B has been studied in detail (Corey & Myers, 1985; Nakanishi et al., 1971; Yamane et al., 1979) many similarities among the various types of antheridiogens can be seen from the standpoint of physiology. Antheridiogens are all water soluble, are active in very low concentrations, and are formed by large, meristic gametophytes. At present, the term pheromone is preferred over the term hormone when speaking of antheridiogens (Nif, 1979). Although much has been accomplished, many questions may still be pursued through laboratory experiments. In contrast to the multitude of laboratory-oriented studies, only a few publications have focused on the occurrence and importance of antheridiogen in natural fern populations. The first publication giving evidence for the natural role of antheridiogen was that of Tryon & Vitale (1977). By mapping gametophytes on natural sites Tryon & Vitale (1977) could show that there was

The sexual nature of Equisetum gametophytes has been problematic for many years and is still not settled. Hauke (1967) and Duckett (1970) gave good reviews of earlier studies on Equisetum gametophytes. There is now general agreement that some spores grow into small, sparsely plated,' antheridial gametophytes and others into larger, copiously plated, archegonial gametophytes. The latter subsequently produce antheridial lobes, and thus become bisexual (Hauke, 1969; Duckett, 1970, 1972). Antheridial gametophytes are usually shorter-lived than archegonial or bisexual gametophytes. There is a red pigment associated with antheridium formation, either in antheridial gametophytes or in antheridial lobes of bisexual gametophytes (Hauke & Thompson, 1973). LaRoche (1967) disagrees with the interpretation of bisexuality in Equisetum. He believes that the gametophytes are dioecious, and vegetatively propagate a second gametophyte generation, which may differ sexually from the first. Davis (1973) states that sex in Equisetum is environmentally induced and not genetically fixed, and Duckett (1970) more or less concurs. In an attempt to understand sexual determination in Equisetum gametophytes, various workers have grown them in culture under various conditions (Schratz, 1928; Orth, 1934; Wollersheim, 1957a, b; Hauke, 1968, 1969, 1971; Duckett, 1970, 1972; Ram & Chatterjee, 1970; Davis, 1973). LaRoche (1967) studied E. arvense gametophytes grown on various media, with varying pH and other external conditions. His results were expressed in time of development of antheridia, archegonia, and sporophytes, and he never spoke to the relative numbers of one sex or the other. Duckett (1970, 1972) was directly concerned with the percentage of antheridial gametophytes. Using isolated cultures in test tubes, he studied nine different species of Equisetum and the influence of three different media on their sexual development. His cultures were maintained for a year or longer. Ram and Chatterjee (1970), using both isolation cultures and mass cultures, studied the effects of pH, percent agar, yeast extract, chemical growth regulators, crowding, varying sucrose concentrations, and light intensity. They reported results as percent male, female, bisexual, or vegetative. Stephan (1928) apparently was the first to grow Equisetum gametophytes on agar in a defined medium. He was also the first to study the effect of light quality and intensity on Equisetum gametophyte development. Klebs (1917) earlier had studied the effect of blue and red light on fern gametophyte development (see the review of experimental studies on fern gametophytes by Miller, 1968). Orth (1934) used isolation cultures of Equisetum arvense and E. fluviatile to test the effect of a

There is now a fairly extensive vascular crytogam flavonoid literature and there are a number of researchers actively engaged in this research field (Swain & Cooper-Driver, 1973). All vascular crytogam flavonoid work has been done on the sporophyte generation, with one exception: Laurent (1966) determined that Blechnum brasiliense gametophytes produced the flavonoid kaempferol, which is one of the flavonoids produced by the B. brasiliense sporophyte. Reasons for the paucity of information on fern gametophyte flavonoids include the easy accessibility of sporophytes and the now disreputed opinion that flavonoids, being associated with lignin synthesis, are exclusive to vascularized plant bodies. This exclusivity has been lost because flavonoids have been isolated and identified in various non-vascular plant groups: certain algal divisions, bryophytes (Swain, 1974), and fern gametophytes (Laurent, 1966). Initially our investigation was undertaken to determine if Dryopteris intermedia A. Gray and D. marginalis A. Gray gametophytes produce flavonoids and, if so, were these the same flavonoids produced by their sporophytic counterparts (Petersen, 1976). Because of the unusual results of this first portion of the research, the inquiry was amplified to include an analysis of flavonoid content along a developmental profile of the gametophytes. Half-strength White's minimum nutrient medium adjusted to pH 6.0 was used to culture the gametophytes. Liquid cultures were prepared by placing 0.25 g of spores in a 4 1 flask and adding 2 1 of nutrient solution. Separate cultures of D. intermedia and D. marginalis were grown at 22?C under 300 ft-c of illumination from cool-white fluorescent lights in a 12/12 hr diurnal cycle. Gametophytes were harvested and assayed for flavonoids at three developmental stages: (1) pre-antheridial initiation (0 antheridia/gametophyte), (2) antheridial initiation (0 or 1 antheridia/gametophyte), and (3) post-antheridial initiation (4-6 antheridia/gametophyte). Ten-gram samples of harvested gametophytes were immediately extracted in methanol and re-extracted repeatedly until a colorless supernatant was obtained. Concentrated extracts were spotted onto Whatman 3MM chromatography paper (42 x 55 cm). Chromatograms were developed in two dimensions employing the two standard solvent systems for the separation of flavonoids: t-butanol, acetic acid, water (3:1:1) for the first dimension and 15% acetic acid, water for the second dimension. Completed chromatograms were inspected under UV light, both in the presence and absence of NH3. Spot color changes under both conditions were noted and R tvalues determined. Spots were excised, eluted in spectral grade methanol, and UV spectral data obtained using standard procedures (Mabry

Mature gametophytes of Botrychium from nature have been described for several species, including B. dissectum (Bierhorst, 1958), B. japonicum (Nozu, 1954; Nishida, 1955), B. lunaria (Bruchmann, 1906), B. obliquum (Campbell, 1921), B. simplex (Campbell, 1922), and B. virginianum (Jeffrey, 1898; Bierhorst, 1958). The gametophytes are subterranean and are tuberous or somewhat elongate to button-shaped. They vary from 1-3 mm to 5-6 mm long, and even reach 1.5-2 cm in some species. The possession of a "dorsal ridge" in which antheridia are embedded is a typical feature of all the known species. The gametophytes have an associated endophytic fungus, the presence of which presumably is essential for continued growth under natural conditions. Botrychium spores appear to have a dormancy that is not easily overcome. To date, only the spores of B. virginianum (Campbell, 1895), B. ternatum (du Buysson, 1889), and more recently of B. dissectum (Whittier, 1972, 1973a) have been germinated, the last species in axenic culture. The morphology of the B. dissectum gametophytes cultured by Whittier (1972) fits the description for B. dissectum from nature, except for the presence of the endophytic fungus. Sucrose and other additives in the medium presumably replaced the contribution of the fungus under natural conditions. The gametophytes, when sexually mature, were only a few millimeters long. Whittier (1973a) has shown that light inhibits spore germination in B. dissectum. He found that a minimum of 3-4 weeks in darkness is necessary for germination to occur after eight weeks in culture. Increasing the length of the dark period increased the percentage of germination. It is interesting to note that Whittier (1973b) showed that six months of darkness were required for the germination of Psilotum spores. In this paper we will describe the morphology of Botrychium multifidum (Gmel.) Rupr. gametophytes as grown on a defined medium in axenic culture. The gametophytes of B. multifidum have never been observed carefully in nature.

Asexually-reproducing gametophytes of the four tropical fern genera Hymenophyllum, Trichomanes, Grammitis, and Vittaria occur in the uplands of the southeastern United States (Farrar, 1967). The most common and abundant of these is the Appalachian Vittaria gametophyte, which Farrar (1978) has described in detail. Dr. A. J. Sharp of the University of Tennessee was the first to find and collect the Appalachian Vittaria gametophyte in the area of the Mountain Lake Biological Station in Virginia. Since that time, Dr. W. H. Wagner, Jr. of the University of Michigan collected it in the same area and catalogued it into a pteridophyte flora (Wagner, 1963). Other pteridologists have collected it in the area of the Highlands Biological Station in North Carolina (Wagner et al., 1970; Pittillo et al., 1975) and in Tennessee (Wofford & Evans, 1979). Other collections have located these gametophytes in several eastern states in and around the southern Appalachians (Farrar, 1978; Gastony, 1977). Appalachian Vittaria gametophytes are long-lived and produce extensive colonies in deep, protected crevices of non-calcareous rock. Although antheridia and archegonia are produced on the gametophytes, reduced, juvenile sporophytes have been found only once in the field by Farrar (1978). They were recognizable as Vittaria, but lacked sufficient characters for identification to species. Since most taxonomic characters for determining fern species are based on sporophyte morphology, the origin and affinities of these gametophytes are uncertain. They were first assigned to the genus Vittaria by Wagner and Sharp (1963) based on finding similar morphological characters between the gametophytes of the Appalachian Vittaria and those of Vittaria lineata (L.) J. E. Smith from Florida. The chromosome counts reported by Gastony (1977) have provided further evidence of their relationship. The experimental production of sporophytes might provide additional taxonomic characters for comparison with the Vittaria species. Farrar (1978) reported that Appalachian Vittaria gametophytes were difficult to maintain in axenic culture and ceased to grow on defined media. We report here successful axenic culture of the Appalachian Vittaria gametophyte and the spontaneous formation of callus and sporophytes.

Most homosporous ferns produce hermaphroditic, haploid gametophytes which arise from a single haploid spore by a series of mitotic divisions. As a result, the male and female gametes from a single gametophyte are genetically identical, barring mutations. Therefore, sporophytes produced by self-fertilization (fusion of sperm and egg from a single gametophyte) can be considered to be genetically homozygous. Although most species produce gametophytes which have the capability for hermaphroditism, several factors of their reproductive biology influence the probability of self-fertilization occurring. These factors include time of maturation of archegonia relative to antheridia, orientation of archegonial necks, density and spatial arrangement of gametophytes (especially when coupled with an antheridogen or other chemical substance which increases the number of unisexual male gametophytes in the population), and presence of deleterious recessive genes which are lethal or sublethal in the homozygous condition (genetic load as used here) and which can prevent production of viable sporophytes following selfing (Klekowski & Lloyd, 1968; Klekowski, 1969a, 1971; Lloyd, 1974a, b, c). Due to the ability of fern gametophytes to form completely homozygous zygotes, it is possible to screen sporophytes for deleterious recessive genes which are active following syngamy and in the first stages of sporophyte ontogeny (Figs. 19-23). These genes are usually expressed as abortive zygotes, abortive embryos which appear as swollen tissue within the archegonium, small and abnormal sporophytic tissue, or abnormalities in the production of the first few fronds or roots (Ganders, 1972). Data of this type, when correlated with gametangia ontogeny, antheridogen studies, and population dynamics of the gametophyte generation have allowed us to sample populations of plants and to determine their probable mating systems and relative degrees of genetic heterozygosity. To date, only a few species have been sampled intensively, including Osmunda regalis (Klekowski, 1970a, 1973) and Ceratopteris thalictroides (Klekowski, 1970b). In some cases it has been possible to predict patterns of population variability and to correlate specific mating systems with specific ecological parameters (Lloyd, 1974b). Two levels of mating are recognized in homosporous ferns, intragametophytic and intergametophytic. Intragametophytic selfing is by definition self-fertilization within single gametophytes with the resulting intralocus genetic homozygosity. Intergametophytic mating results in various levels of heterozygosity depending on the origin of the gametes. Fusion of gametes originating from separate gametophytes but these in turn from spores of a single sporophyte (inter

Nephrolepis cordifolia (L.) Presl is a native of the West Indies and is found as an escape from cultivation in this country only in the state of Florida. It is similar in many respects to the common Boston fern (N. exaltata var. bostoniensis). It differs in two respects: the more nearly erect position of the leaves and the fronds (PI. 6, fig. 1), and in the formation of tubers (Pl. 6, fig. 2) by means of which the plant may be reproduced. Propagules of this nature are formed in only a few other ferns, but are, no doubt, familiar to most readers of the Journal. The reproduction of the fern has been studied by the writer for several years and will be briefly described. As in all other ferns which belong to the Polypodiaceae, the fronds of N. cordifolia bear numerous spores from each of which upon germination is produced the sexual phase or the gametophyte generation, the small heartshaped prothallium familiar to every one interested in ferns. As is well known, the prothallium bears on its under surface the sex-organs (antheridia and archegonia) which produce the gametes, the sperms and the eggs. After fertilization, the asexual phase, or sporophyte generation is formed. About three years later, the plant, thus formed, reaches maturity, when it produces

Studies of the gametophyte generation of Equisetum have occupied botanists ever since Vaucher (1821) first reported the germination of spores and illustrated early stages in gametophyte development. Buchtien (1887) summarized the knowledge of gametophytes up to his time. Gametophytes have occasionally been found and described from naturally occurring populations (Kashyap, 1914; Walker, 1921, 1931; Mackel, 1924; Schratz, 1928). All except Schratz reported that wild gametophytes bear archegonia at first, with some subsequently producing antheridia. Schratz, however, counted 848 wild gametophytes and stated that 46.9% were male and 53.1% were female or, in a few cases, bisexual.

Schraudolf (1962, 1964) and Voeller (1964a, b) have demonstrated that young gametophytes of 12 species of ferns in the Schizaeaceae form antheridia when supplied with gibberellic acid (GA). Hormonal concentrations of seven different gibberellic acids, GA7, GA4, GA3, GAg, GA1, GA5, and GA8, in order of decreasing relative activity, have been shown to be strikingly active in initiating formation of male reproductive organs in Anemia phyllitidis (L.) Swartz. In contrast, gibberellic acid has little or no effect on the gametophytes of a wide range of species from other families, such as the Blechnaceae, Pteridaceae, Polypodiaceae, Osmundaceae, Cyatheaceae, Davalliaceae, or Aspidiaceae (Voeller, 1964a, b). In a remarkable variety of respects, the effects of gibberellic acid on Anemia phyllitidis are indistinguishable from the effects of the naturally occurring antheridium-inducing hormone, antheridogen-B, produced by A. phyllitidis: (i) the two substances each show specificity of organ induction, i.e., antheridia are induced, but archegonia, rhizoids, papillae, etc., are not; (ii) the time interval between application of and response to either hormone is quite similar; (iii) the sequence of cell divisions giving rise to the organ is the same, and the resultant sperms swim actively and are apparently functional; (iv) and the dosage-response curve of the antheridogen is distinctive and paralleled by that for gibberellic acid.