Chemical variation in Notholaena standleyi

In Notholaena standleyi (Pteridaceae), differences in geographic range, aspect, height, edaphic requirements, and the color and chemistry of the ceraceous exudate on the abaxial side of the frond suggest at least three distinct subgroups of this taxon. One race, with a light yellow exudate consisting mostly of kaempferol, 3-O-methylkaempferol and 4'-O-methylkaempferol occurs in the eastem portion of the range. A yellow-green race and a gold race possess mostly 7-0methylkaempferol and 4'-O-methylkaempferol but also the uncommon compounds 7-0-methylherbacetin and 7,4'-di-O-methylherbacetin. Plants of the yellow-green race produce minor constituents with methyl substituents in the 3-position whereas those of the gold race lack them. Plants of this last group produce only traces of kaempferol. Principal Components Analysis based on nine flavonoid constituents and 59 samples was carried out. Plants of the three groups clustered in plots of Principal Components 1 vs. 2, 1 vs. 3, and 2 vs. 3 and were separated from each other. These plants reproduce ameiotically and thus there is little or no gene flow among them and they are geographically distinct. We prefer to maintain them as informally recognized taxa pending further studies. NOTHOLAENA STANDLEYI Maxon (Peteridaceae), a xeric fern of the southwestern United States and northern Mexico, is one of several species which produces a dense exudate or farina (often called 'ceraceous') primarily on the abaxial surface of the fronds. Plants occur on dry rock ledges and in crevices, on talus slopes, cliffs, canyon walls, and on or among boulders up to 2,200 m elevation, from southeastern Colorado to Texas and southern Nevada and south to east-central Mexico (Correll and Johnston, 1970). Notholaena standleyi is a member of a group of ferns with distributions and relations centered on the arid Mexican plateau. This group is a part of the exceptional and probably ancient xeric flora that has evolved in response to the development of aridity in Mexico and the adjacent U.S. (R. Tryon, 1969 and 1972; and Tryon and Tryon, 1973). The type specimen (Bigelow, Kew; photo at the Gray Herbarium) was collected at La Cuesta, New Mexico and first described by Hooker (1864) as Notholaena candida var. quinquefi1 Received 24 May 1982; revision accepted 2 August 1982. We acknowledge the financial support of the Research Board of the University of Illinois (D.S.) and the Deutsche Forschungsgemeinschaft (E.W.), thank G. N. May, T. E. Lockwood, G. Sarmiento and L. Gurga for assistance during the early stages of this work, G. Yatskievych for a bulk sample of N. standleyi, and the curators of several herbaria for making materials available to us. We also appreciate the assistance of Dr. R. B. Selander and Kevin Spencer with the numerical analysis. do-palmata. In Eaton's account (1878-1879) (not based on the type), he described the characteristic yellow powder on the lower frond surface and included an excellent illustration ofthe fern. The currently accepted name, Notholaena standleyi was proposed by Maxon in 1915. Notholaena standleyi has at times been confused with N. sulphurea but differs in that the pinnae above the basal pair are connected at the base so that the lamina is deeply pinnatifid whereas in N. sulphurea, the pinnae are free and the lamina is fully pinnate (R. Tryon, 1956). Individuals of Notholaena standleyi generally have 32 spores per sporangium, but several with 16 spores have been observed (R. Tryon, 1956). Specimens collected in Maricopa and Pima Co., Arizona had 32 spores and, 2n = 60 chromosomes (Knobloch, Tai and Ninan, 1973; A. Smith, 1974). Although most ferns that have 32 spores per sporangium which have been examined have proven to be apogamous and are derived from eight 4n spore mother cells (Manton, 1950, 1958; A. Tryon, 1968), members of this taxon produce spores from eight 2n spore mother cells (A. Smith, 1974) in a manner similar to that previously described for Polypodium dispersum Evans (Evans, 1964). The farinose coating of these plants is not excreted by the entire epidermis as a true wax coating, but is formed exclusively by the globose terminal cell of small trichomes which