Tempskya
... that the stems in the pseudo-trunk of the extinct fern Tempskya decayed as the plant matured, leaving a layer of adventitious roots behind?
... that the <a href="./Plant_stem" id="mwAT8" rel="mw:WikiLink" title="Plant stem">stems</a> in the pseudo-<a href="./Trunk_(botany)" id="mwAUA" rel="mw:WikiLink" title="Trunk (botany)">trunk</a> of the extinct <a href="./Fern" id="mwAUE" rel="mw:WikiLink" title="Fern">fern</a> <i id="mwAUI"><b id="mwAUM"><a href="./Tempskya" id="mwAUQ" rel="mw:WikiLink" title="Tempskya">Tempskya</a></b></i> <a href="./Decomposition" id="mwAUU" rel="mw:WikiLink" title="Decomposition">decayed</a> as the plant matured, leaving a layer of <a href="./Root#Specialized_roots" id="mwAUY" rel="mw:WikiLink" title="Root">adventitious roots</a> behind?