Spore morphology of the representatives of the subfamily Ceratopteridoideae (J. Sm.) R.M. Tryon from the family Pteridaceae E.D.M. Kirchn. (Pteridophyta)

Abstract

<p>Scanning electron microscopy (SEM) was used to perform a comparative study for four representatives of the subfamily <em>Ceratopteridoideae</em> (J. Sm.) R.M. Tryon from East Asia: <em>Ceratopteris thalictroides</em> Brongn., <em>C. pteridoides</em> (Hook.) Hieron., <em>Acrostichum aureum</em> Linn., and <em>A.</em> <em>speciosum </em>Willd. The analysis of the external morphology of the representatives of <em>Ceratopteridoideae</em> revealed a strong difference between <em>Ceratopteris</em> and <em>Acrostichum</em>.</p><p>The external morphology of spores of <em>Ceratopteris</em> and <em>Acrostichum</em> exhibited the features characterizing the family Pteridaceae as a whole: tetrahedral spores with a three-ray laesure, from triangular-roundish to roundish, distinct exosporium with a pronounced surface ornamentation and absence of perisporium, the exosporium surface varying from smooth and rough to that covered with large tubercles and roller-like bulges.</p><p>The external morphology of spores of <em>Acrostichum</em> is quite simple, although among other representatives of the family Pteridaceae,<em> </em>the<em> </em>spores of <em>Ceratopteris</em> have distinctive features: very large equatorial diameter (106–124 µm); spores are almost roundish; distinct cylindrical folds running parallel to the corners of the spore across its extensive distal surface.</p><p> </p>