Observations of the spore, gametophyte and young sporophyte of Pteridium caudatum (L.) Maxon using scanning electron microscopy.

This paper describes the development of the sexual phase of the invasive fern, Pteridium caudatum, from spore germination to young sporophyte formation. Spores samples for gametophyte cultures were taken from various sporophytes and then sown on mineral agar with Thompson's media. Gametophytes were maintained under fluorescent light on a 12h light, 12h dark cycle at 24-25°C. Developmental phases were fixed in FAA-sucrose solution and processed for observation with the scanning electron microscope. Spores are trilete and germination takes place on the second day after sowing; germination is of the Vittaria-type. Adiantum-type prothallial development was observed. The differentiation of a two-dimensional thallus begins 5 days after germination maturation of adult gametophytes occurs about 30 days after sowing. Adult gametophytes are heart-shaped, bisexual and glabrous. Antheridia are formed by three cells: basal, annular and opercular cell with a pore. Archegonia have a neck of 4-cells. The young sporophyte becomes visible within 8 weeks after spores are sown. The taxonomic significance of the gametophyte morphology is discussed.