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

Abstract

Scanning electron microscopy (SEM) was used to perform a comparative study for four representatives of the subfamily Ceratopteridoideae (J. Sm.) R.M. Tryon from East Asia: Ceratopteris thalictroides Brongn., C. pteridoides (Hook.) Hieron., Acrostichum aureum Linn., and A. speciosum Willd. The analysis of the external morphology of the representatives of Ceratopteridoideae revealed a strong difference between Ceratopteris and Acrostichum. The external morphology of spores of Ceratopteris and Acrostichum 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. The external morphology of spores of Acrostichum is quite simple, although among other representatives of the family Pteridaceae, the spores of Ceratopteris 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.