Hippuris
Hippuris vulgaris
mare's-tail
common mare's-tail, hippuride vulgaire, mare's tail
(2–)3–5 mm diam.
erect, glabrous.
100–400 mm.
cauline, whorled;
petiole absent;
blade not fleshy, not leathery (fleshy or leathery in H. tetraphylla), margins entire.
on mid portions of emergent shoots in whorls of (7 or)8 or 9(–12), linear to narrowly oblong or lanceolate, 3–35 × 0.5–2.5 mm, midvein inconspicuous, lateral veins present, sometimes obscure, apex subacute to acute or attenuate, tip often curled in dried plants.
axillary, flowers solitary;
bracts absent.
present (proximal) or absent (distal);
bracteoles absent.
bisexual or unisexual;
calyx a minute rim adhering to summit of inferior ovary;
petals 0;
stamen 1, adnate to ovary, filaments glabrous;
staminode 0;
ovary 1-locular, placentation apical;
stigma linear along surfaces of style.
bisexual;
filaments longer than anthers.
drupes.
1.5–2 × 0.8–1 mm.
1, brownish, globular, wings absent.
= 8.
= 32.
Hippuris
Hippuris vulgaris
Species 4 (4 in the flora).
Leaf characteristics of Hippuris used here are derived from whorls on the emergent portions of the stems; morphology of submerged leaves differs sharply from that of emergent shoots.
M. E. McCully and H. M. Dale (1961) proposed that the taxa treated below all could be expressions of phenotypic plasticity of Hippuris vulgaris developed in different regimes of salts and photoperiod; this was not accepted by E. Hultén (1973), nor is it accepted here. Number of leaves in a whorl varies among plants and even on the same stem. Nevertheless, there are clear limits and discontinuities in leaf number and shape among taxa, which are well-correlated with less variable characters as well as with ecology and geography.
Hippuris has been placed in Halagoraceae or in Hippuridaceae as a monogeneric family. Molecular phylogenetic studies now place it in Plantaginaceae (D. C. Albach et al. 2005).
(Discussion copyrighted by Flora of North America; reprinted with permission.)
Hippuris vulgaris is the most common and widespread species of Hippuris; it is largely absent from the Canadian Arctic Archipelago and Greenland. All specimens seen by the authors from that region are H. lanceolata.
The distribution of Hippuris vulgaris is bipolar, occurring also in southern South America (Patagonia: Argentina and Chile) and Australia; it exists in some areas as a naturalized introduction, possibly from being used in aquaria and ornamental pools. In Australia, H. vulgaris is monitored for its potential to become noxious by spreading rapidly in shallow waterways.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
1. Flowers unisexual; leaves 2–10 mm, midveins often conspicuous, lateral veins absent; stems 15–100 mm; rhizomes 1 mm diam. | H. montana |
1. Flowers bisexual; leaves 3–35 mm, midveins inconspicuous, lateral veins present, sometimes obscure; stems 80–500 mm; rhizomes (2–)3–7 mm diam. | → 2 |
2. Leaves on mid portions of emergent shoots in whorls of (7 or)8 or 9(–12), tips often curled in dried plants; filaments longer than anthers. | H. vulgaris |
2. Leaves on mid portions of emergent shoots in whorls of 3–6(or 7), tips not curled in dried plants; filaments equal to or shorter than anthers. | → 3 |
3. Leaves on mid portions of emergent shoots in whorls of (5 or)6(or 7), linear to narrowly oblong or lanceolate, 0.5–1.5 mm wide, apices subacute. | H. lanceolata |
3. Leaves on mid portions of emergent shoots in whorls of 3–5(or 6), oblanceolate or oblong to broadly obovate, 2–8 mm wide, apices obtuse, rounded, or blunt. | H. tetraphylla |
- Local floras:
CA, 
OR, 
WA - Local Web sites: CalFlora, CalPhotos,
Flora NW, 
PNW Herbaria 
WildflowerSearch
iNaturalist (observations)
USDA Plants Database- LBJ Wildflower Center
- SEINet
- Plants of the World Online
- Encyclopedia of Life
- Wikipedia
- Google Image Search
- Local floras:
BC, CA, OR, WA - Local Web sites: CalFlora, CalPhotos, Flora NW,
Go Botany, 
IL Wildflowers, 
MI Flora, 
MN Wildflowers, PNW Herbaria, 
SW CO Wildflowers - WildflowerSearch
- iNaturalist (observations)
- USDA Plants Database
- LBJ Wildflower Center
- SEINet
- Plants of the World Online
- Encyclopedia of Life
- Wikipedia
- Google Image Search
