Polypodium vulgare versus P. virginianum in the Eastern United States

Abstract

Fosberg's (1968) report of the European Polypodium vulgare L. on the coastal plain of the northeastern United States is of significance to the phytogeographical study of the P. vulgare complex in North America and Europe. Fernald (1922) enumerated the main morphological differences between P. virginianum L. and P. vulgare L. These include an acrid tasting rhizome, scales with sagittate attachment, and submarginal sori in P. virginianum, as opposed to a sweet rhizome, peltately attached rhizome scales, and medial sori in P. vulgare. The most characteristic feature of P. virginianum was found to be the glandular paraphyses described by Martens (1943, 1950) and by Martens and Pirard (1943). The only other possible report of true P. vulgare in eastern North America is a herbarium specimen dealt with by Martens (1943). The plant in question (from the Antwerp Botanical Garden) was mounted on the same herbarium sheet as a plant with paraphyses collected in Philadelphia in 1824. Martens concluded that the non-paraphysate P. vulgare specimen had been added to the sheet at a later date from a European locality. No occurrence of P. vulgare in eastern North America is mentioned in the works of Manton (1950) or Shivas (19 6 la, b) on the cytogenetics of the P. vulgare complex in Europe, nor by Manton (1950, 1951, 1957), Manton and Shivas (1953), or Evans (1971) in their studies of North American P. virginianum. All the aforementioned works stress the separate distributions of P. vulgare and P. virginianum. Fosberg, in recording P. vulgare from Long Island, Suffolk County, New York, based his identification on the fact that the sori bore no paraphyses, and the habitat-a sandy slope of glacial origin-was one that was more typical of the European species. Fernald (1922) had previously noted that P. virginianum is ordinarily a plant of rock habitats, only rarely occurring as an epiphyte; no mention of sandy banks was made. This viewpoint has been repeated by various authors, e.g., Cobb (1956) and House (1924). The question of whether the Long Island P. vulgare was indigenous or had been introduced with European trees planted in the area was raised by Fosberg. In my work on pteridophytes of Suffolk County, I reinvestigated the site of Fosberg's discovery on December 27, 1974, accompanied by G. Paul Kemp. This was made possible by Mrs. Grosvenor Atterbury, the owner, who kindly showed us the location, as she had Dr. Fosberg in 1968. The colony is on the northeast slope of a small glacial hill in the Shinnecock Hills of eastern Long Island at an elevation of ca. 65 ft (not 65 m, as reported earlier). The dominant trees at this