Comparative Research of Gametophytes ofOlfersia alataandOlfersia cervina(Dryopteridaceae)

Abstract

The prothallial development of gametophytes of Olfersia alata and Olfersia cervina (Dryopteridaceae) is described and compared. Spores are monolete, ellipsoid, and with broadly winged perispore. Germination is Vittaria-type and the prothallial development is Aspidium- type. Adult gametophytes are cordiform-spatulate to cordiform-reniform, with marginal and superficial trichomes. Gametangia are of the type commonly found on leptosporangiate homo- sporous ferns. Differences between the two species of genus include size of the spores, width of the perispore, germination time, size of the trichomes, and time of formation of the gametangia. These two species share some features with some species of Arachniodes, Cyrtomium, Dryopte- ris, Phanerophlebia, and Polystichum, such as type of germination and prothallial development and trichomes. They differ from Didymochlaena truncatula, which has prothallial development of the Adiantum-type and lacks trichomes on the sexual phase. The genus Olfersia Raddi (Dryopteridaceae), has two species: Olfersia alata C. Sanchez & Garco´a Caluff and Olfersia cervina (L.) Kunze. Olfersia alata is endemic to Cuba; its main characteristics are all sterile pinnae have decurrent bases, and fertile leaves which are smaller and have fewer pinna pairs than the vegetative leaves. It grows in mountainous mesophytic forests, between 350-400 m (Sanchez et al., 1991). Olfersia cervina is widely distrib- uted in the tropics, from Southern Mexico (Chiapas, Oaxaca, Veracruz), to Southeastern Brazil and the West Indies. In this species the bases of the ster- ile pinnae are not decurrent onto the rachis, and pinnae are short-petiolu- late. It grows between 450-1000 m in damp tropical forests, on rocky and very shady banks (Moran, 1986, 1995; Riba and Perez-Garco´a, 1999). Both taxa are usually terrestrial, rarely hemiepiphytic, with a short trailing rhi- zome. Leaves are markedly dimorphic, sori are exindusiate and linear to ob- long, and spores are monolete, echinulate with a broad perispore. This paper complements existing information about the morphogenesis of the gametophytic phase of dryopteriod ferns and, particulary, focuses on gametophytes of Olfersia. We hope to contribute in this way to the knowledge of the sexual phase of Mexican ferns.