Hydrostachys

 Hydrostachys is a genus of about 22 species[2] 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-moving water. They have tuberous roots, usually pinnately compound leaves, and highly reduced flowers on dense spikes.[3]

Hydrostachys
Hydrostachys imbricata.jpg
Hydrostachys imbricata
Scientific classificatione
Kingdom:Plantae
Clade:Tracheophytes
Clade:Angiosperms
Clade:Eudicots
Clade:Asterids
Order:Cornales
Family:Hydrostachyaceae
Engl.[1]
Genus:Hydrostachys
Thouars
Species

Approximately 22; see text.

Phylogenetic 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. 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.[3][4] Its position in Cornales is uncertain; it may be basal to the rest of the order, or fall within the family Hydrangeaceae.[3][5][6] It shares few morphological similarities with other Cornales.[3]

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 Metasyntactic variable, which is released under the 
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