| Hydrostachys | |
|---|---|
 | |
| Hydrostachys imbricata | |
Scientific classification | |
| Kingdom: | Plantae |
| Clade: | Tracheophytes |
| Clade: | Angiosperms |
| Clade: | Eudicots |
| Clade: | Asterids |
| Order: | Cornales |
| Family: | Hydrostachyaceae Engl.[1] |
| Genus: | Hydrostachys Thouars |
| Species | |
Approximately 22; see text. | |
Hydrostachys is a genus of about 22 species[2] offlowering plants native toMadagascar and southern and centralAfrica. It is the only genus in the familyHydrostachyaceae. All species ofHydrostachys are aquatic, growing on rocks in fast-moving water. They have tuberous roots, usuallypinnately compound leaves, and highly reduced flowers borne on dense spikes.[3]
The phylogenetic placement ofHydrostachys is particularly problematic. Owing to its specialized aquatic morphology, it has often been grouped with other aquatic plants, such as those in the familyPodostemaceae. However, embryological, floral, and other morphological characters do not support this placement, and molecular data suggest thatHydrostachys is related to taxa in the orderCornales.[3][4] Its position within Cornales remains uncertain; it may be basal to the rest of the order or may fall within the familyHydrangeaceae.[3][5][6] It shares few morphological similarities with other members of Cornales.[3]
(This list may be incomplete.)
