Dichotomous Key/Polypodiopsida

Nature print, Alois Auer.jpg Alois Auer Plantae Embryophyta Embryophyta Polypodiopsida Polypodiopsida Glossary for this page (all links are to Wikipedia articles)Bipinnate: Leaf arrangement where the leaflets of a pinnate leaf are also pinnately divided. Also called "twice pinnate".Midrib: The central, most prominent vein of a leaf or leaflet.Pinna(e): Leafy segment of a single pinnate blade, sometimes appearing to be an individual leaf.Pinnule: Ultimate free leaflet of a multi-pinnate leaf.Rachis: The main stem of a compound leaf.Spine: A stiff, sharp structure; usually a modified leaf or stem.Sporophyll: A modified leaf that bears the plant's spores. A fern is a member of a group of vascular plants that reproduce via spores and have neither seeds nor flowers. They differ from mosses by being vascular, i.e., having certain tissue that conducts water and nutrients, and having branched stems. Like other vascular plants, ferns have leaves, and these are "megaphylls", which are more complex than the "microphylls" of clubmosses. Most ferns are leptosporangiate ferns, sometimes termed "true ferns"; they produce what are called "fiddleheads" that uncoil and expand into fronds.Jim McCausland http://www.sunset.com/garden/flowers-plants/rediscover-ferns-00400000016579/ Rediscover ferns Sunset.com 20 September 2009 2013-09-07 The group includes about 10,560 known extant species.Christenhusz, M. J. M. Byng, J. W. 2016 The number of known plants species in the world and its annual increase Phytotaxa 261 201–217 http://biotaxa.org/Phytotaxa/article/download/phytotaxa.261.3.1/20598 10.11646/phytotaxa.261.3.1 3 Magnolia Press Ferns first appear in the fossil record 360 million years ago in the late Devonian period,http://www.ucmp.berkeley.edu/plants/pterophyta/pteridofr.html Pteridopsida: Fossil Record University of California Museum of Paleontology 2014-03-11 but many of the current families and species did not appear until roughly 145 million years ago in the early Cretaceous, after flowering plants came to dominate many environments. The fern Osmunda claytoniana is a paramount example of evolutionary stasis; paleontological evidence indicates it has remained unchanged, even at the level of fossilized nuclei and chromosomes, for at least 180 million years.Bomfleur B, McLoughlin S, Vajda V Fossilized nuclei and chromosomes reveal 180 million years of genomic stasis in royal ferns Science 343 6177 1376–7 March 2014 24653037 10.1126/science.1249884 References