Variations in Petiolar Structure of Hypodematium crenatum

Abstract

The importance of leaf traces in fern taxonomy has been discussed in detail by Tansley (1907, 1908), Sinnott (1911), Davie (1918), Ogura (1972), and others. Ching (1936) differentiated between Thelypteris and Dryopteris on the basis of petiolar characters. Bower (1914) used these characters along with others in establishing the relationships between Blechnum and allied genera. Sen (1964), Keating (1968), and Lucansky (1974a, 1974b) also used petiolar characters in working with dennstaedtioid, cyatheoid, dicksonioid, and pteroid ferns as did Bir (1962) and Kato (1972, 1975) in differentiating members of Athyriaceae. Recently, Lin and DeVol (1977, 1978) have given a key, based entirely on petiolar characters, to 170 species of Taiwan ferns and tried to establish relationships between various families of extant ferns. The above literature and many other references show that petiolar characters, particularly vascular pattern, are relatively constant within a species. In order to test constancy in Indian ferns, we have tried to study materials of the same taxon collected from diverse localities (see Khare, 1984; Khare & Shanker, 1984, 1986). In the process we noted that Hypodematium crenatum (Forssk.) Kuhn (Aspidiaceae of Copeland, 1947) showed considerable variation among the petioles of plants collected from different sites. A detailed study of their petioles was then begun.