01756nas a2200133   4500008004100000245007900041210006900120490000700189520132200196100002101518700002101539700001801560856004401578       2016                        eng d00aMegaspores of an early Miocene aquatic lycopod (Isoetales) from Antarctica0 aMegaspores of an early Miocene aquatic lycopod Isoetales from An0 v553 aThe paucity of late Paleogene and Neogene floras from Antarctica limits our ability to understand the interplay between Antarctic climate evolution and the impact that glaciation had on the vegetation, in particular, how the vegetation changed from temperate Eocene forests, to today’s sparse vegetation. Fluvial and lacustrine strata deposited in a wet-based glacial sequence (Friis Hills, McMurdo Dry Valley sector, Transantarctic Mountains) have yielded abundant megaspores. These strata are early Miocene based on correlation with a volcanic ash dated at 19.76 ± 0.11 Ma. The megaspores are up to 736 μm in diameter with well-developed wing-like laesurae and equatorial zona. The morphology is consistent with extant Isoetes, and demonstrates the presence of Lycopsida and the Isoetaceae within Antarctic Miocene floras. Today, Isoetes is widespread from the Tropics to the Arctic such as Greenland (I. echinospora, I. lacustris) and from marginal marine (I. ekmanii) to high altitudinal environments (I. lechleri), though commonly associated with lacustrine or aquatic environments. The fossil spores occur in fluvial and lacustrine beds, suggesting the parent plants were aquatics. The occurrence together with mosses and Nothofagus leaves points to persistent vegetation in the early Miocene of Antarctica.1 aCantrill, D., J.1 aAshworth, A., C.1 aLewis, A., R.  uhttps://isoetes.myspecies.info/node/23302028nas a2200265   4500008004100000245015000041210006900191260001200260300001200272490000700284520111700291653004701408653002001455653002101475653002001496653002301516653002001539653000801559653001101567653002201578100001401600700001401614700001701628856011701645       2012                        eng d00aMicromorphological approach to the systematics of Mediterranean Isoëtes species (Isoëtaceae, Lycopodiophyta): Analysis of the megaspore surface0 aMicromorphological approach to the systematics of Mediterranean   c2012///  a35 - 430 v513 aMegaspore ornamentation is one of the few morphological characters used in the taxonomy of the genus Isoëtes. In the present work, we test the application of this character for distinguishing some Isoëtes species occurring in the Mediterranean: Isoëtes sicula, which according to some authors should be included as a variety in I. histrix, and the recently described I. todaroana, whose affinity with other taxa is currently unknown. Two additional species (I. duriei, I. velata) were also included in the analysis. The megaspores were studied using scanning electron microscopy combined with energy-dispersive X-ray spectroscopy and chemical treatment. In all species, the megaspore surface is covered by a siliceous coating; removal of this coating reveals an underlying three-dimensional network of fused rodlets. A unique pattern of this network occurs in I. sicula, supporting its separation from I. histrix. Comparison between the patterns observed in the examined Mediterranean species shows that I. todaroana is most similar to I. histrix. © 2012 Copyright 2012 Collegium Palynologicum Scandinavicum.10aenergy-dispersive X-ray spectroscopy (EDS)10aIsoëtes duriei10aIsoëtes histrix10aIsoëtes sicula10aIsoëtes todaroana10aIsoëtes velata10aSEM10aSicily10asiliceous coating1 aTroia, A.1 aBazan, G.1 aSchicchi, R.  uhttp://www.scopus.com/inward/record.url?eid=2-s2.0-84859208191&partnerID=40&md5=8268047dea3226ff247ba747f4878e5d01741nas a2200205   4500008004100000245010200041210006900143260001200212300001200224490000700236520105300243653001301296653001401309653002601323100001801349700001801367700001501385700001801400856011701418       2012                        eng d00aDevelopment of megaspores and microspores in Isoetes japonica A. Br. (Lycopodiophyta: Isoetaceae)0 aDevelopment of megaspores and microspores in Isoetes japonica A   c2012///  a84 - 960 v513 aMicrospore and megaspore development in Isoetes japonica was studied using light, scanning electron and transmission electron microscopy. Differences in cytokinesis following meiosis result in monolete microspores with bilateral symmetry, and trilete megaspores with radial symmetry. Wall development follows essentially the same sequence in both microspores and megaspores, but with the wall of the latter being very much thicker. A significant difference was observed in the tetrad stage, when microspores have an essentially rounded outline with the plasma membrane folded into a crest at the site of the future aperture. Megaspores in the tetrad stage are strongly invaginated over their entire surface, creating numerous crests, and this appears to have a role in determining the morphology of the perispore. The outline shape of the megaspore perispore having been established in the tetrad stage, most of its substance is added later and is derived from the degenerating tapetum. © 2012 Copyright 2012 Collegium Palynologicum Scandinavicum.10aexospore10aperispore10asporoderm development1 aBlackmore, S.1 aTakahashi, M.1 aUehara, K.1 aWortley, A.H.  uhttp://www.scopus.com/inward/record.url?eid=2-s2.0-84863571691&partnerID=40&md5=f7e81951aa6adcdbb44db83d38c686dd