FLAVONOIDS OF THE PRIMITIVE FERNS: STROMATOPTERIS, SCHIZAEA, GLEICHENIA, HYMENOPHYLLUM, AND CARDIOMANES

The flavonoids of the primitive leptosporangiate ferns Stromatopteris moniliformis, Schizaea bifida, Gleichenia cunninghamii, Cardiomanes reniforme, and Hymenophyllum demissum have been identified as 3-0-glycosides of the flavonols kaempferol and quercetin. None of the examined ferns produced flavonoids which are also common to the Psilotoceae. The Psilotaceae have previously been shown to produce 0-glycosides of amentoflavone (biflavone) and apigenin (flavone) and traces of C-glycosylflavones (Wallace and Markham, 1978). These data imply that the primitive leptosporangiate ferns are not closely related to the Psilotaceae. The antiquity of rhamnose as a glycosyl moiety is suggested by its occurrence in both the primitive leptosporangiate ferns and in the Psilotaceae. SEVERAL interpretations of fern phylogeny have been published (Pichi-Sermolli, 1973). All have considered the Schizacaceae, Gleicheneaceae, Stromatopteridaceae, and Hymenophyllaceae as representing primitive leptosporangiate ferns. Most previous authors considered the Psilotaceae to represent a distinct and only remotely related taxon. However, Bierhorst (1968, 1977) challenged the position of the Psilotaceae as being a well defined entity at the divisional level. He reclassified the Psilotaceae, containing both Psilotum and Tmesipteris, into the Pteridophyta where it was closely allied with the monotypic Stromatopteridaceae. He supported this by detailed morphological studies involving ontogeny of both sporophytes and gametophytes. Most convincing were the anatomical comparisons of young sporophytes of Psilotum, Tmesipteris and Stromatopteris as well as his observation of an "annulus" on the psilotaceous synangium. However, as evidenced at a recent symposium, many morphologists are not in agreement (White, 1977; Gensel, 1977; Kaplan, 1977; Wagner, 1977). Subsequently Cooper-Driver (1977) presented phytochemical evidence that the Psilotaceae should not be allied with Stromatopteris or any other primitive (or advanced) fern. She contended that I Received for publication 28 March 1978; revision accepted 5 July 1978. The authors are grateful to Dr. Phillip Morat, Noumea, New Caledonia, and to Dr. Patrick Brownsey, The National Museum, Wellington, New Zealand for supplying Stromatopteris moniliformis. J.W.W. acknowledges the support of a New Zealand National Research Advisory Council Senior Research Fellowship and a Faculty Research Grant from Western Carolina University. the presence of amentoflavone as the only flavonoid in both Psilotum and Tmesipteris with the corresponding absence of flavonols was justification to keep the Psilotaceae as a separate entity at the divisional level. Recently Wallace and Markham (1978) documented the total flavonoid profile of species of Psilotum and Tmesipteris. They identified amentoflavone and its 0-glycosides as the major components of both genera and reported the presence of flavone-O-glycosides as minor constituents with C-glycosylflavones occurring as trace components. Although amentoflavone and its 0-glycosides have not been documented in ferns, it is known that some ferns have the ability to synthesize flavone 0-glycosides (Swain and Cooper-Driver, 1973) and C-glycosylflavones (Ueno et al., 1963; Soeder and Babb, 1972). Interestingly, a full analysis of the flavonoid glycosides of Stromatopteris and other primitive leptosporangiate ferns has not as yet been published. The present paper is a detailed account of the flavonoids of Stromatopteris moniliformis, Schizaea bifida, Gleichenia cunninghamii, Cardiomanes reniforme, and Hymenophyllum demissum. Phylogenetic implications of these compounds pertaining to the relationship of the primitive leptosporangiate ferns to themselves and to the Psilotaceae will be discussed. MATERIALS AND METHODS-Plant materialsStromatopteris moniliformis Mett. (14.0 g d.w.) was collected in March 1977, at Noumea, New Caledonia; Schizaea bifida Willd. (1.8 g d.w.) was collected on 12 April 1977, Auckland, New