leptosporangiate

The development and structure of the gametophytes show some similar characteristics between the sister group Acrostichum and Ceratopteris: 1) Spore germination is of the Vittaria-type; 2) Prothallial developments is of the Ceratopteris-type; 3) Young prothalli are markedly lopsided; 4) Gametangia are the common leptosporangiate type.

Fern phylogeny inferred from 400 leptosporangiate species and three plastid genes.

Antheridia were typical of leptosporangiates; when mature, they produced and released sperm cells (Fig.

This is one of the most common patterns of germination within leptosporangiates, and it has been cited as usual in the Pteridaceae (Nayar & Kaur 1969, 1971).

The remaining living ferns consist of heterosporous leptosporangiate genera that are either amphibious (Marsileales) or floating aquatics (Salviniales; Gifford & Foster, 1989).

These include 13 extant homosporous filicaleans, 17 extinct homosporous and heterosporous ferns from Paleozoic strata, five extant and one extinct heterosporous leptosporangiate ferns, two extant marattiaceous ferns, two extant ophioglossaceous ferns, one extant and two extinct equisetophytes, both extant homosporous psilotophytes (i.e., Psilotum and Tmesipteris), one extinct heterosporous progymnosperm, three extinct and one extant seed plants, and the extinct homosporous trimerophyte Psilophyton crenulatum (Appendix 1).