Marsileales
The order Marsileales is an order of
ferns in the Division Pteridophyta. They are all aquatic and differ from all other ferns in being
heterosporous, meaning that they produce two different types of
spores that develop into two different types of gametophytes , and in that their gametophytes are endosporic, meaning that they never grow outside the spore wall and cannot become larger than the spores that produced them. In being heterosporus with endosporic gametophytes they are more similar to
seed plants than to other ferns.
The
ferns of this order vary radically in form from one another and do not look particularly fern-like.
Encyclopedia
The order
Marsileales is an order of
ferns in the Division Pteridophyta. They are all aquatic and differ from all other ferns in being
heterosporous, meaning that they produce two different types of
spores that develop into two different types of gametophytes , and in that their gametophytes are endosporic, meaning that they never grow outside the spore wall and cannot become larger than the spores that produced them. In being heterosporus with endosporic gametophytes they are more similar to
seed plants than to other ferns.
The
ferns of this order vary radically in form from one another and do not look particularly fern-like. Species of the families
Azollaceae and
Salviniaceae are natant , while those of the family
Marsileaceae are rooted. However, the natant species may temporarily grow on wet mud during times of low water, and the Marsileaceae may grow as emergent species, depending on species and location.
There is a well-known
fossil member of the Marsileales,
Hydropteris .
