Megaspore development in Selaginella. I. ?Wicks?, their presence, ultrastructure, and presumed function

Development of megaspores and microspores inIsoetes japonicaA. Br. (Lycopodiophyta: Isoetaceae)

“…In contrast, individual microspores have a maximum length of 5 µm (along the equatorial axis) in the early tetrad stage to 25-28 µm at maturity. These results are very consistent with those reported in Selaginella by Morbelli and Rowley (1993), Rowley and Morbelli (1995) and Morbelli et al (2003).…”

“…Morbelli & Rowley, 1993;Rowley & Morbelli, 1995Rowley et al, 2002). With the modesty that was such a feature of John Rowley's character, Rowley and Morbelli (1995, p. 133) described their study of development in Selaginella megaspores as 'a humbling undertaking'.…”

“…Then, as now, the majority of pteridophytes studied were ferns, with only a limited sampling of Lycopodiophyta. Previous studies of sporogenesis in Lycopodiophyta have investigated Lycopodium sensu lato (Lugardon, 1976;Pettitt, 1966Pettitt, , 1971bRowley, 1995), Selaginella (Pettitt, 1971b;Robert, 1971aRobert, , 1971bRobert, , 1971cSievers & Buchen, 1971;Lugardon, 1972;Buchen & Sievers, 1978a, 1978b, 1981Brown & Lemmon, 1985;Taylor, 1991;Morbelli & Rowley, 1993, 1999Hemsley et al, 1994;Morbelli, 1995;Rowley & Morbelli, 1995Rowley et al, 2002;Morbelli et al, 2003;Moore et al, 2006) and Isoetes (Lugardon, 1973(Lugardon, , 1990Robert et al, 1973;Brown & Lemmon, 1989Taylor, 1992).…”

Megaspore morphology in the Selaginellaceae in a phylogenetic context: A study of the megaspore surface and wall structure using scanning electron microscopy

“…Hemsley and co-workers first focused on the grid-like pattern, but have expanded the idea to also include the more unordered structures (Hemsley et al 1998). Further studies like these, together with developmental studies (such as Taylor, 1991;Morbelli & Rowley, 1993Rowley & Morbelli, 1995;Morbelli et al 2003) will probably play an important role in understanding the exospore structure in Selaginella megaspores, and, as a consequence, help in the interpretation of homologous features.…”

“…These are usually based on light microscopy or scanning electron microscopy and present surface morphology (e.g., Reeve, 1935;Tryon, 1949;Hellwig, 1969), sometimes also including structures of the exospore wall (Morbelli, 1977;Stafford, 1991;Morbelli et al 2001). Ultrastructural features of the megaspore wall and megaspore ontogeny have been the subject of other studies (e.g., Martens, 1960a, b;Stainier, 1965;Pettitt, 1966;Stainier, 1967;Kempf, 1970;Sievers & Buchen, 1970;Tryon & Lugardon, 1978;Taylor, 1987;Taylor & Taylor, 1987;Taylor, 1991;Hemsley et al 1992;Collinson et al 1993;Morbelli & Rowley, 1993;Taylor, 1994;Morbelli, 1995;Rowley & Morbelli, 1995;Morbelli & Rowley, 1996;. Generally one or a few species have been examined in each study, using scanning and transmission electron microscopy.…”