''Hydrostachys'' is a genus of about 22 species of

flowering plant Flowering plants are plants that bear flowers and fruits, and form the clade Angiospermae (), commonly called angiosperms. The term "angiosperm" is derived from the Greek words ('container, vessel') and ('seed'), and refers to those plants t ...

s native to

Madagascar Madagascar (; mg, Madagasikara, ), officially the Republic of Madagascar ( mg, Repoblikan'i Madagasikara, links=no, ; french: République de Madagascar), is an island country in the Indian Ocean, approximately off the coast of East Afric ...

and southern and central

Africa Africa is the world's second-largest and second-most populous continent, after Asia in both cases. At about 30.3 million km2 (11.7 million square miles) including adjacent islands, it covers 6% of Earth's total surface area ...

. It is the only genus in the family Hydrostachyaceae. All species of ''Hydrostachys'' are aquatic, growing on rocks in fast-moving water. They have tuberous roots, usually pinnately compound leaves, and highly reduced flowers on dense spikes.Albach, D. C., Soltis, D. E., Chase, M. W., and Soltis, P. S. (2001). Phylogenetic placement of the enigmatic angiosperm ''Hydrostachys''. Taxon 50, 781-805.

Phylogenetic In biology, phylogenetics (; from Greek φυλή/ φῦλον [] "tribe, clan, race", and wikt:γενετικός, γενετικός [] "origin, source, birth") is the study of the evolutionary history and relationships among or within groups ...

placement of ''Hydrostachys'' is particularly problematic. Due to its specialized aquatic morphology, it has often been grouped with other aquatic plants, such as the family

Podostemaceae Podostemaceae (riverweed family), a family in the order Malpighiales, comprise about 50 genera and species of more or less thalloid aquatic herbs. Distribution and habitat They are found mostly in tropical and subtropical areas worldwide. Ma ...

. However, embryological, floral, and other morphological characters do not support this placement, and molecular data suggest that ''Hydrostachys'' is related to taxa in the order

Cornales The Cornales are an order of flowering plants, early diverging among the asterids, containing about 600 species. Plants within the Cornales usually have four-parted flowers, drupaceous fruits, and inferior to half-inferior gynoecia topped with ...

. Its position in Cornales is uncertain; it may be basal to the rest of the order, or fall within the family

Hydrangeaceae Hydrangeaceae is a family of flowering plants in the order Cornales, with a wide distribution in Asia and North America, and locally in southeastern Europe. Description The genera are characterised by leaves in opposite pairs (rarely whorled ...

.Fan, C. Z., and Xiang, Q. Y. (2003). Phylogenetic analyses of Cornales based on 26S rRNA and combined 26S rDNA-matK-rbcL sequence data. ''American Journal of Botany'' 90, 1357-1372.Kubitzki, K. (2004). Cornaceae. In ''The Families and Genera of Vascular Plants Volume 6: Flowering Plants: Dicotyledons: Celastrales, Oxidales, Rosales, Cornales, Ericales'' (Kubitzki, ed.). Springer-Verlag, New York. It shares few morphological similarities with other Cornales.

Species

(This list may be incomplete.) * '' Hydrostachys decaryi'' * '' Hydrostachys distichophylla'' * '' Hydrostachys fimbriata'' * '' Hydrostachys imbricata'' * ''

Hydrostachys laciniata ''Hydrostachys'' is a genus of about 22 species of flowering plants native to Madagascar and southern and central Africa. It is the only genus in the family Hydrostachyaceae. All species of ''Hydrostachys'' are aquatic, growing on rocks in fast ...

'' * ''

Hydrostachys longifida ''Hydrostachys'' is a genus of about 22 species of flowering plants native to Madagascar and southern and central Africa. It is the only genus in the family Hydrostachyaceae. All species of ''Hydrostachys'' are aquatic, growing on rocks in fast ...

'' * ''

Hydrostachys maxima ''Hydrostachys'' is a genus of about 22 species of flowering plants native to Madagascar and southern and central Africa. It is the only genus in the family Hydrostachyaceae. All species of ''Hydrostachys'' are aquatic, growing on rocks in fast ...

'' * ''

Hydrostachys monoica ''Hydrostachys'' is a genus of about 22 species of flowering plants native to Madagascar and southern and central Africa. It is the only genus in the family Hydrostachyaceae. All species of ''Hydrostachys'' are aquatic, growing on rocks in fast ...

'' * ''

Hydrostachys multifida ''Hydrostachys'' is a genus of about 22 species of flowering plants native to Madagascar and southern and central Africa. It is the only genus in the family Hydrostachyaceae. All species of ''Hydrostachys'' are aquatic, growing on rocks in fast ...

'' * ''

Hydrostachys perrieri ''Hydrostachys'' is a genus of about 22 species of flowering plants native to Madagascar and southern and central Africa. It is the only genus in the family Hydrostachyaceae. All species of ''Hydrostachys'' are aquatic, growing on rocks in fast ...

'' * ''

Hydrostachys plumosa ''Hydrostachys'' is a genus of about 22 species of flowering plants native to Madagascar and southern and central Africa. It is the only genus in the family Hydrostachyaceae. All species of ''Hydrostachys'' are aquatic, growing on rocks in fast ...

'' * ''

Hydrostachys stolonifera ''Hydrostachys'' is a genus of about 22 species of flowering plants native to Madagascar and southern and central Africa. It is the only genus in the family Hydrostachyaceae. All species of ''Hydrostachys'' are aquatic, growing on rocks in fast ...

'' * ''

Hydrostachys trifaria ''Hydrostachys'' is a genus of about 22 species of flowering plants native to Madagascar and southern and central Africa. It is the only genus in the family Hydrostachyaceae. All species of ''Hydrostachys'' are aquatic, growing on rocks in fast ...

'' * ''

Hydrostachys verruculosa ''Hydrostachys'' is a genus of about 22 species of flowering plants native to Madagascar and southern and central Africa. It is the only genus in the family Hydrostachyaceae. All species of ''Hydrostachys'' are aquatic, growing on rocks in fast ...

References

External links

''Hydrostachys'' on eFloras.org
{{Taxonbar, from1=Q285630, from2=Q1136814 Hydrostachyaceae Cornales genera