Editing Psilotum (section)

==Description and life cycle==
Whisk ferns in the genus ''Psilotum'' lack true roots but are anchored by creeping [[rhizome]]s. The stems have many branches with paired [[enation]]s, which look like small leaves but have no [[vascular tissue]]. Above these enations there are synangia formed by the fusion of three [[Sporangium|sporangia]] and which produce the [[spore]]s. When mature, the synangia release yellow to whitish spores which develop into a [[gametophyte]] less than {{convert|2|mm|in|sigfig=1|abbr=on}} long. The gametophyte lives underground as a mycoheterotroph, tapping into mycorrhizal networks to access carbon and other nutrients. When the gametophyte is mature, it is [[monoicous]], producing both egg and sperm cells. The sperm cells swim using several [[Flagellum|flagella]] and when they reach an egg cell, unite with it to form the young [[sporophyte]]. A mature sporophyte may grow to a height of {{convert|30|cm|in|sigfig=1|abbr=on}} or more but has no apparent<ref name="Friedman-et-al-2004" /> leaves. The stem has a core of thick-walled [[Stele (biology)#Protostele|protostele]] in its centre surrounded by an [[endodermis]] which regulates the flow of water and nutrients. The surface of the stem is covered with [[stoma]]ta which allow gas exchange with the surroundings.<ref name="Fairley">{{cite book|last1=Fairley|first1=Alan|last2=Moore|first2=Philip|title=Native plants of the Sydney region : from Newcastle to Nowra and west to the Dividing Range|date=2010|publisher=Allen & Unwin|location=Crows Nest, N.S.W.|isbn=9781741755718|page=16|edition=3rd}}</ref><ref name="UCMP">{{cite web|title=Introduction to the Psilotales|url=http://www.ucmp.berkeley.edu/plants/pterophyta/psilotales.html|publisher=University of California Museum of Paleontology|access-date=24 December 2016}}</ref><ref name="RBGS">{{cite web|title=''Psilotum''|url=http://plantnet.rbgsyd.nsw.gov.au/cgi-bin/NSWfl.pl?page=nswfl&showsyn=&dist=&constat=&lvl=gn&name=Psilotum|publisher=[[Royal botanic Gardens Sydney}]]: plantnet|access-date=24 December 2016}}</ref>

The gametophyte of ''Psilotum'' is unusual in that it branches dichotomously, lives underground and possesses vascular tissue.<ref name="Holloway">{{cite journal|last1=Holloway|first1=John E.|title=The Gametophyte, Embryo, and Young Rhizome of ''Psilotum triquetrum'' (Swartz)|journal=Annals of Botany|date=1939|volume=3|issue=2|pages=313–336|doi=10.1093/oxfordjournals.aob.a085063}}</ref>  The nutrition of the gametophyte appears to be [[myco-heterotrophs|myco-heterotrophic]], assisted by [[endophyte|endophytic]] [[fungi]].<ref name="Manton">{{cite journal|last1=Manton|first1=Irene|title=A Note on the Cytology of Psilotum with Special Reference to Vascular Prothalli from Rangitoto Island|journal=Annals of Botany|date=1942|volume=6|issue=2|pages=283–292|doi=10.1093/oxfordjournals.aob.a088408}}</ref><gallery>
File:Psilotum nudum Rhizome.jpg|''Psilotum nudum'' rhizomes
File:Psilotum nudum Sydney Opera House.JPG|Clump of ''Psilotum nudum'' plants
File:Psilotum complanatum - Lyman Plant House, Smith College - DSC04275.JPG|''Psilotum complanatum'' plant
</gallery>