Variations in Microsporangia and Microspore Dispersal in Selaginella

Abstract

Fifty‐three species of Selaginella were examined for variations in microsporangium anatomy and microspore dispersal strategies. Five anatomically different kinds of microsporangia were observed, displaying three different strategies for microspore dispersal. Xeric species, including all isophyllous species, have microsporangia that only dry and shrink as they dehisce, resulting in microspores being passively dispersed. Among anisophyllous species from tropical and subtropical habitats some species actively eject their microspores, while others of the series Articulatae eject the entire microsporangium. These two types of active ejection both utilize a mechanism similar to that found in fern leptosporangia.

The sub-arborescent lycopsid Omphalophloios feistmantelii (O. Feistmantel) comb. nov. emend. from the Middle Pennsylvanian of the Czech Republic

“…Consequently, the relevant detailed information (such as the number of cell layers, cell pattern and opening mechanism) about sporangium cellwall character was often omitted or marginalized because the predominant opinion among botanists was that sporangial cell-wall character lacked taxonomical importance for lycopsids. The present study reflects the importance of such features as the number of cell layers, cell pattern and sporangial opening mechanism congruent with studies of the extant Selaginella species, which show that sporangial cell-wall character has value in taxonomical classification (Somers 1982, Koller & Scheckler 1986. In neither of the cited papers did the authors mention some clearly specialized cells as an opening mechanism.…”

“…Similar structures are described by Koller & Scheckler (1986) from microsporangia of extant Selaginella Beauvoir species. According to Koller & Scheckler (1986) dehiscence in species of the living lycopsid Selaginella begins when cells of the mature microsporangium dry, causing a contraction of the outer layer of cells sufficient enough to split adaxial and abaxial valves apart. Nevertheless, the sclerenchymatous strips, which are 100-200 μm wide, rather disrupt the dehiscence area into shreds.…”

“…36. Microsporangia of O. feistmantelii show a two-wall cell pattern similar to that of the Selaginella microsporangia described by Koller & Scheckler (1986). The detail of epidermal cells of Omphalophloios-type of sporangia is resulting from obtaining large pieces of cuticle from sporangia.…”

Speed and force of spore ejection in Selaginella martensii

“…Both microspores and megaspores are dispersed actively. In the case of microspores, tetrads are the dispersal units (Koller and Scheckler 1986).…”

“…Knowledge about mechanisms of microspore discharge is more recent. Koller and Scheckler (1986) distinguished three types of microspore dispersal. The first type consists in a passive dispersal of microspores.…”