Fertile Sporophytes of Botrychium virginianum Attached to Gametophytes

Abstract

While making a floristic survey of the pteridophytes of the Highlands, North Carolina area (Macon County) with Dr. Warren H. Wagner, Jr., I discovered a population of Botrychium virginianum containing many small but fertile specimens. An apparently similar population has been described for the I\Iountain Lake (Giles County) area in Virginia (Wagner, 1963, pp. 130-131.) Investigation of the Macon County plants showed a considerable percentage of the plants attached to large gametophytes. Whereas juvenile plants typically are found attached to a gametophyte (Bierhorst, 1958), the plants found near Highlands showed a wide range of developmental stages. Many were fully fertile with small leaves 3-5 cm broad (Fig. 1). These juvenile specimens have had the name B. virginianum var. gracile (Pursh) Lawson applied to them, but are not worthy of taxonomic recognition (Weatherby, 1935). Precociously fertile sporophytes may be due to abundant nutrition supplied by long-lived gametophytes. Gametophytes of most ferns usually die after the sporophyte has become self-sufficient. This is not strictly the case in the eusporangiate genus Botrychium where gametophytes have been reported still attached to sporophytes at least two years old (Foster, 1964) and up to eight years old (Jeffrey, 1896-97, pp. 271272). Campbell (1911, p. 18) mentions that fertile B. virginianum sporophytes with attached gametophytes were found by Jeffrey, but similar plants are not mentioned by later workers. Bierhorst (1958) believes that a relatively small number of gametophytes persist after giving rise to a sporophyte. He states that in areas where sporophytes of all ages are present it is not the older sporophytes with attached gametophyte which predominate,