Hippuris lanceolata
Hippuris
hippuride à feuilles lancéolées, lance-leaf mare's-tail
mare's-tail
4–7 mm diam.
100–500 mm.
erect, glabrous.
on mid portions of emergent shoots in whorls of (5 or)6(or 7), linear to narrowly oblong or lanceolate, 5–20 × 0.5–1.5 mm, midvein inconspicuous, lateral veins present, sometimes obscure, apex subacute, tip not curled in dried plants.
cauline, whorled;
petiole absent;
blade not fleshy, not leathery (fleshy or leathery in H. tetraphylla), margins entire.
axillary, flowers solitary;
bracts absent.
present (proximal) or absent (distal);
bracteoles absent.
bisexual;
filaments equal to or shorter than anthers.
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.
drupes.
1.8–2 × 0.6–1.2 mm.
1, brownish, globular, wings absent.
= 8.
= 32 (Russian Far East).
Hippuris lanceolata
Hippuris
N. N. Tzvelev (1980) speculated that Hippuris lanceolata arose from hybridization between H. tetraphylla and H. vulgaris or their precursors. Although H. lanceolata is intermediate in some features, and is often misplaced with either H. tetraphylla or H. vulgaris, it is fertile and there is no indication of pollen abortion or failure of seed set. No transitional plants have been seen; hybrid origin appears unlikely. The range of H. lanceolata extends well north of that of either putative parent, especially that of H. vulgaris. Hippuris lanceolata is the sole species of Hippuris in some areas of the Arctic.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
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.)
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 |
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