''Pilularia'' or pillworts is a genus of unusual

fern The ferns (Polypodiopsida or Polypodiophyta) are a group of vascular plants (plants with xylem and phloem) that reproduce via spores and have neither seeds nor flowers. They differ from mosses by being vascular, i.e., having specialized tissue ...

s of family

Marsileaceae Marsileaceae () is a small family of heterosporous aquatic and semi-aquatic ferns, though at first sight they do not physically resemble other ferns. The group is commonly known as the "pepperwort family" or as the "water-clover family" becau ...

distributed in North Temperate regions,

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n mountains, and the southern hemisphere in

Australia Australia, officially the Commonwealth of Australia, is a country comprising mainland Australia, the mainland of the Australia (continent), Australian continent, the island of Tasmania and list of islands of Australia, numerous smaller isl ...

New Zealand New Zealand () is an island country in the southwestern Pacific Ocean. It consists of two main landmasses—the North Island () and the South Island ()—and List of islands of New Zealand, over 600 smaller islands. It is the List of isla ...

, and western

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. Depending on the taxonomic revisor, the genus contains between 3 and 6 species of small plants with thread-like leaves, and creeping rhizomes. The

sporangia A sporangium (from Late Latin, ; : sporangia) is an enclosure in which spores are formed. It can be composed of a unicellular organism, single cell or can be multicellular organism, multicellular. Virtually all plants, fungus, fungi, and many ot ...

are borne in spherical sporocarps ("pills") which form in the

axil A leaf (: leaves) is a principal appendage of the stem of a vascular plant, usually borne laterally above ground and specialized for photosynthesis. Leaves are collectively called foliage, as in "autumn foliage", while the leaves, stem, fl ...

s of leaves. ''

Pilularia minuta ''Pilularia minuta'' is a species of fern in the family Marsileaceae. It is an ephemeral species that relies on seasonal flooding. Though widely distributed across the Mediterranean basin, it is considered an endangered species due to habitat f ...

'' from SW Europe is one of the smallest of all ferns.

Phylogeny

Recent work from Pryer Lab accepted four species of ''Pilularia'', with a fifth, ''P. novae-zealandiae'', being conspecific with ''P. novae-hollandiae''. In addition, another species, ''P. dracomontana'', has been described from

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References

UK Biodiversity Action Plan
* Preston, C.D. & Croft, J.M. (1997). ''Aquatic Plants in Britain and Ireland''. Harley Books, pp. 31–32.

External links

Salviniales Fern genera {{Polypodiidae-stub