Hydrostachys
Encyclopedia
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-moving water. They have tuberous roots, usually pinnately compound leaves, and highly reduced flowers on dense spikes.
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
. Its position in Cornales is uncertain; it may be basal to the rest of the order, or fall within the family Hydrangeaceae
. It shares few morphological similarities with other Cornales.
Madagascar
The Republic of Madagascar is an island country located in the Indian Ocean off the southeastern coast of Africa...
and southern and central Africa
Africa
Africa is the world's second largest and second most populous continent, after Asia. At about 30.2 million km² including adjacent islands, it covers 6% of the Earth's total surface area and 20.4% of the total land 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.
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
Podostemaceae
The Podostemaceae is a family in the order Malpighiales. It comprises about 50 genera and 250 species of more or less thalloid aquatic herbs....
. 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
Cornales
Cornales is an order of flowering plants, basal among the asterids, containing about 600 species. Plants within Cornales usually have four-parted flowers, drupaceous fruits, and inferior gynoecia topped with disc-shaped nectaries...
. Its position in Cornales is uncertain; it may be basal to the rest of the order, or fall within the family Hydrangeaceae
Hydrangeaceae
Hydrangeaceae are a family of flowering plants in the order Cornales, with a wide distribution in Asia and North America, and locally in southeastern Europe.-Overview:...
. It shares few morphological similarities with other Cornales.