A COMPARATIVE STUDY OF THE MORPHOLOGY AND ANATOMY OF LEUCOSTEGIA AND ARAIOSTEGIA

The anatomy and morphology of Leucostegia immersa (Wall.) Presl (type species of the genus Leucostegia) and Araiostegia pulchra (Don.) Copel. (a species which comes very near to the type species of the genus Araiostegia) are described in detail for the first time in order to determine whether the genus Araiostegia is distinct from Leucostegia. The present investigation reveals that Leucostegia differs from Araiostegia in many significant morphological and anatomical details. For example, in Leucostegia , both scales and hairs protect the rhizome, while on the rhizome of Araiostegia hairs are absent. Further, the basifixed scales of Leucostegia are sharply different from the strongly peltate scales of Araiostegia. Though the stelar cylinders in the two genera are basically similar in construction, they are markedly different in their modes of production of root-traces and leaf-traces. No tanniniferous cells which are found in Leucostegia , occur in the fundamental tissues of Araiostegia. Young fronds of Leucostegia produce delicate hairs, but in Araiostegia the fronds are glabrous throughout. The rachises and costae in Leucostegia are grooved on the upper surface and never show any raised median bands in sharp contrast to the rachises of Araiostegia which are at least in the upper part narrowly winged on either side of the raised upper surface. All these differences certainly show that these genera are well defined. The relationship between Araiostegia and other davallioid ferns is also discussed.