Plants annual, submerged in fresh water. Rhizome absent. Stems terete to slightly compressed, ca. 0.8 mm in diam., sparsely to densely branched; nodal glands absent or inconspicuous; turions markedly reduced, axillary, usually narrowly fusiform. Stipules axillary, free, 5-12 mm, connate, membranous and translucent, tubular for most of their length when young, but splitting with age, not fibrous-persistent, green or greenish brown when dry; leaves sessile, linear, 2-6 cm × 0.6-2.3 mm, 3-veined with lateral veins inconspicuous, mostly without rows of lacunae bordering midvein, midvein distinctly thickened toward leaf base, apex acute to acuminate. Spikes with 2-4 whorls of opposite flowers, lax. Carpels 4. Fruit obliquely obovoid, 1.8-2.2 mm, abaxial keel indistinct, with a short beak at tip. Fl. and fr. May-Oct. 2n = 26.
Rhizomes absent. Cauline stems terete to slightly compressed, without spots, 18--150 cm; glands present on at least some nodes, green, gold, brown, or rarely white, to 0.5 mm diam. Turions common, soft, lateral or terminal, 0.9--3.2 cm ´ 0.3--1.8 mm, soft; leaves ± 2-ranked; outer leaves 1--3 per side, base not corrugate, apex subulate to obtuse; inner leaves rolled into hardened fusiform structure. Leaves submersed, ± spirally arranged, sessile, delicate to coarse; stipules persistent, inconspicuous, connate or convolute, free from base of blade, brown to green or white, not ligulate, 0.31--0.92 cm, rarely appearing fibrous, not shredding at tip, apex obtuse; blade pale green to olive-green, rarely somewhat reddish, linear, not arcuate, 0.9--6.5 cm ´ 0.2--2.5 mm, base slightly tapering, without basal lobes, not clasping, margins entire, not crispate, apex not hoodlike, subulate to obtuse, lacunae absent or present, in 0--5 rows each side of midrib; veins 1--3(--5). Inflorescences unbranched, submersed or emersed; peduncles not dimorphic, axillary or terminal, erect, rarely recurved, filiform to slightly clavate, 0.5--6.2(--6.6) cm; spikes not dimorphic, capitate to cylindric, 1.5--10.1 mm. Fruits sessile, green to brown, ovoid to obovoid, turgid to concave, not abaxially or laterally keeled, 1.5--2.2 ´ 1.2--1.6 mm; beak erect, 0.1--0.6; sides without basal tubercles; embryo with less than 1 full spiral.
7. Potamogeton pusillus L., Sp. Pl. 127 (1753). Lectotipo (designado por Dandy y Taylor, 1938): Europa, Anon. (microficha MEXU! ex LINN-175.15).
Por A. Novelo R. y A. Lot H.
Potamogeton pusillus L., Sp. Pl. 127. 1753.
Hojas sumergidas, delicadas, lineares, 1.46.5 cm de largo y 0.51.9 mm de ancho, con 13 nervios, sésiles. Inflorescencias sumergidas o emergentes, axilares, 2.510.1 mm de largo y 1.24.7 mm de diámetro, con 24 verticilos de flores; pedúnculos 16.2 cm de largo. Fruto 1.52.2 mm de largo y 1.21.5 mm de ancho, sin quilla.
Conocida en Nicaragua solamente de una laguna artificial en Selva Negra, Matagalpa; 1200 m; fl y fr probablemente durante todo el año; Haynes 8262, Stevens 17835; Alaska hasta el sur de Sudamérica, también en Europa. La especie ha sido separada en 4 variedades, la población de Nicaragua pertenece a P. pusillus var. pusillus.
Perenne, totalmente sumergida, con turiones. Hojas sésiles, la lámina 1.5–8.5 cm × (0.4–)1–2.8 mm, lin-ear o ligulada, delicada, con un banda de lagunas ca. 0.2 mm de ancho (hasta ca. 1/4 el ancho de la lámina).Infls. axilares; fls. en 3–5 verticilos ampliamente espaciados, emergentes. Frs. 1.7–2(–2.8) × 1–1.5(–1.8) mm,engrosados, sin una quilla dorsal; pico ca. 0.5 mm, conspicuo.
Stems very slender, to 1.5 m, with numerous branches distally, with or without nodal glands; rhizome scarcely developed; lvs all submersed, narrowly linear, 1–7 cm × 0.2–2.5 mm, 1- or 3(5)-veined, with 0–5 rows of lacunar cells on each side of the midvein; stipular sheaths axillary, free, to 1 cm, delicate, the margins connate or merely overlapping; winter-buds commonly produced, 1–3 cm, the inner lvs rolled into a hard, fusiform structure; peduncles filiform to slightly clavate, axillary or terminal, mostly erect, 0.5–6 cm; spikes capitate to cylindric, 2–10 mm, with 1–4 whorls of fls; body of the fr ovoid to obovoid, usually plump, not keeled, 1.5–2.2 mm, the beak 0.1–0.6 mm; 2n=26. Common and widespread in both acid and alkaline waters from Nf. to Alas., s. to Fla. and Mex. Highly variable. (P. berchtoldii; P. panormitanus; P. tenuissimus) The most narrow-lvd phase, with subulate, 1-nerved lvs 0.2–0.6 mm wide, considered to be restricted to N. Engl. and s. Que., has been called var. gemmiparus Robbins. (P. gemmiparus)
Rhizomes absent; erect stems terete to slightly compressed, without spots, 18-150 cm long. Leaves submersed, sessile, ± spirally arranged, delicate to coarse, entire, noncrisped, pale green to olive, rarely rufescent, linear, nonarcuate, l-3(-5)-veined, 0.9-6.5 x 0.2-2.5 mm, lacunae absent or to 5 rows each side of midrib, the apex noncucullate, subulate to obtuse, the base without basal lobes; glands present or absent, green, gold, brown, or rarely white, to 0.5 mm diam.; ligules inconspicuous, free from base of blade, nonligulate, brown to green or white, rarely appearing fibrous, not shredding at tip, connate or convolute, 3.1-9.2 mm long, the apex obtuse. Turions common, soft, lateral or terminal, 0.9-3.2 cm x 0.3-1.8 mm; inner leaves rolled into a hardened fusiform structure; outer leaves 1-3 per side, subulate or obtuse, without corrugations at base. Inflorescences unbranched; peduncles all similar, filiform to slightly clavate, axillary or terminal, mostly erect, rarely recurved, 0.5-6.2(-6.6) cm long; spikes all similar, capitate to cylindric, 1.5-10.1 mm long. Fruits sessile, ovate to obovate, turgid to compressed, green to brown, without abaxial or lateral keels, 1.5-2.2 x 1.2-1.6 mm; beak erect, 0.1-0.6 mm long; sides without basal tubercles; embryo with less than one full spiral.
Aquatic, perennating with axillary winter-buds. Stem filiform, c. (0.5-) 1 mm broad, branched. Leaves submerged, sessile, linear, 1-2 mm broad, tip tapering or rounded, 3(-5)-veined, midrib without lacunae. Stipules free, 6-8 mm long, 2 mm broad, ovate, acute, entire, membranous, tubular towards the base. Peduncles 1.2-3 cm long; spikes 5 mm long, few flowered, with 2-4, distant whorls. Perianth segments 1-1.5 mm long, 1-2 mm broad, broadly obtuse. Fruitlets c. 2 mm long, 1-1.5 mm broad, obovoid.
It is a very polymorphic species. Plants with wide upper leaves have been called P. subjavanicus. The decision to `lump' it together with P. pusillus has been accepted. It can be distinguished from other linear-leaved species by having stipules which are closed and tubular at the base when young; the midrib occupies 15-35 per cent of the leaf width at the base.
Leaf: leaf submersed present; form of the leaf submersed linear; apex of the leaf submersed acute/apiculate; base of the leaf submersed obtuse/mucronate; petiole of the leaf submersed absent; leaf floating absent; form of the leaf floating absent; apex of the leaf floating absent; base of the leaf floating absent; petiole of the leaf floating absent. Fruit: form of the fruit obovate; carina dorsal absent.
Hoja: hoja(s) submersa(s) presente(s); forma de las hoja(s) submersa(s) linear(es); ápice(s) de las hoja(s) submersa(s) agudo(s)/apiculado(s); base de las hoja(s) submersa(s) obtusa(s)/mucronada(s); pecíolo(s) de las hoja(s) submersa(s) ausente(s); hoja(s) flutuante(s) ausente(s); forma de las hoja(s) flutuante(s) ausente(s); ápice(s) de las hoja(s) flutuante(s) ausente(s); base de las hoja(s) flutuante(s) ausente(s); pecíolo(s) de las hoja(s) flutuante(s) ausente(s). Fruto: forma del fruto(s) obovado(s); carena(s) dorsal(es) ausente(s).
Submerged aquatic herb.
Submerged perennial or annual. Stolons absent or present towards the end of the growing season, thread-like, sometimes developing terminal or axillary bulb-like tubers. Stems up to 100 cm or more long, flattened to almost terete, usually repeatedly branched, sometimes developing terminal or axillary tubers. Leaves submerged; stipules axillary, closed but splitting open later, translucent, 0.4-1.8(-3.2) cm long, persistent or decaying; blades sessile, linear, flattened, (1.5-)2-8.5(-11) cm long, (0.3-)0.8-2.5(-3.1) mm wide, green to brown, 1-, 3-or 5-veined, midrib with poorly developed gas-filled channels along each side or gas-filled channels confined to the basal half of the leaf, or gas-filled channels absent, bases wedge-shaped, margins entire, tips acuminate to subobtuse. Peduncles slender, (0.6-)1-4.5(-8) mm long, usually shorter than the leaves, flexible at first becoming firm in fruit. Spikes cylindrical, 0.4-1.3 cm long in fruit, with 2-7 flowers, ± contiguous. Drupelets usually 4, asymmetrically obovoid, 1.8-2.7(-3.3) mm long, beak less than 0.6 mm long, dorsal keel indistinct.
Biryıllık, rizomsuz, sucul bitkiler. Gövde silindirik veya nadiren silindiriğe yakın, az ya da çok dallanmış, en çok 100 cm boyunda; toprakaltında filiz üretir. Düğümlerde bezeler ya yoktur ya da çok küçüktür. Yapraklar almaşlı dizilişli, sapsız, hepsi batık; yaprak kını yaprak tabanından serbest, en azından alt kısımları kapalı, borucuk biçiminde, 6-14 mm boyunda, zarsı, saçaksız veya saçaklı, genellikle dökülücü; yaprak ayası 3 damarlı, yan damarlar genellikle belirgin değil, 16-56 × 0,8-3 mm, şeritsi; orta damarın her iki tarafı 0-2 adet yivli ya da yivsiz, yaprak tabanına doğru belirgin şekilde şişkin; kenarları düz; tabanı yuvarlak; uçları sivri ilâ küt; üst yapraklar bazen genişlemiş olabilir. Çiçekdurumu sapı 12-36 mm uzunlukta; çiçekdurumu başak, 5-10 mm uzunluğunda, genellikle aralıklı veya kesintisiz. Karpel 4 tane. Meyve genellikle tersyumurtamsı ilâ yuvarlak, 1,9- 2,5 × 1,5-2 mm; gaga kısa, sırt tarafa eğik.
Folha: folha(s) submersa(s) presente(s); forma das folha(s) submersa(s) linear(es); ápice(s) das folha(s) submersa(s) agudo(s)/apiculado(s); base das folha(s) submersa(s) obtusa(s)/mucronada(s); pecíolo(s) das folha(s) submersa(s) ausente(s); folha(s) flutuante(s) ausente(s); forma das folha(s) flutuante(s) ausente(s); ápice(s) das folha(s) flutuante(s) ausente(s); base das folha(s) flutuante(s) ausente(s); pecíolo(s) das folha(s) flutuante(s) ausente(s). Fruto: forma do fruto(s) obovado(s); carena(s) dorsal(ais) ausente(s).
Turions, when present, mostly sessile and axillary, but sometimes terminal on axillary branches, rigid, fusiform, with a few erect, patent or recurved free leaves.
Submerged leaves bright green to olive green or dark green, sometimes with a brownish tinge, sessile, linear, (9– )20– 85(– 110) mm long, (0.3– ) 0.8– 2(– 2.5) mm wide, (15– )20– 90 times as long as wide, flaccid or firm, translucent, narrowly cuneate at base, tapering or rather abruptly narrowed to an acute or acuminate apex; margins entire, bordered by a narrow marginal vein; midrib occupying 15– 35 per cent of the leaf width at base, not bordered by lacunae or the lacunae poorly developed and restricted to the lower leaf half; lateral veins 1(– 2) on each side, distinct, joining the midrib 1.5– 4 leaf widths below the leaf apex; true floating leaves absent but rarely the uppermost leaves with lamina floating at the water surface, subsessile, linear-oblanceolate, 18– 38 mm long, 1.3– 3.1 mm wide, 7– 20 times as long as wide, bright green, narrowly cuneate at base, acute to narrowly obtuse at apex, 3– 5-veined, with broad rows of lacunae bordering the midrib; stipules axillary, connate and forming a tubular sheath at least in their lower part and when young, but splitting with age, 4– 18(– 32) mm long, translucent, persistent or decaying; turions mostly sessile and axillary, but sometimes also terminal on axillary branches, narrowlycylindrical, with a few erect, patent or recurved free leaves.
Rhizomes absent or only present later in the growing season,annual to biennial, filiform, terete, with short internodes.
Peduncles filiform to slightly clavate, ± flexuous, (6– )10– 30(– 55) mm long, 1– 6 times as long as the fruiting spike, as thick as the stem, slightly or distinctly compressed; spikes cylindrical, with 2– 7 flowers, in 1– 4 whorls, ± contiguous, sometimes the lowest flower remote, 4– 15 mm long in fruit.
Tepals 0.8– 1.8 mm long, mostly persistent; carpels (3– )4(– 5); anthers 0.7– 0.9 mm long.
Fruitlets obovoid, ± compressed, 1.8– 2.7 mm long, 1– 1.5 mm broad, green to pale olive, dorsally without keel, beak nearly centrally placed, straight or somewhat oblique, 0.2– 0.4 mm long.
Stem anatomy: stele of the circular type; endodermis of the O-type; interlacunar bundles absent; subepidermal bundles present; pseudo-hypodermis mostly absent, if present 1-layered.
Stems annual to perennial, up to 1 m long, 0.3– 0.7(– 1) mm in diameter, terete or compressed, sparingly to much branched.
Wie P. berchtoldii, aber Blatthäutchen in der unteren Hälfte röhrig verwachsen, später aufreissend. Seitennerven in der Blattspitze spitzwinklig in den Mittelnerv mündend. Blütenstand zylindrisch, Früchte glatt.
Submerged, long-rooted herb. Stems up to 1 m long. Leaves all submerged, very narrow, usually 2 mm wide. Lacunar system bordering midrib not developed or very narrow. Stipule tubular, pale brown. Fruit smooth.
Submerged aquatic. Leaves linear. Flowers green, inconspicuous.
Submerged herbs arising from winter-buds or seed and forming no rhizome or a poorly developed one. Roots long and fine. Stems up to 100 cm, branching from near the base, internodes fairly equal in length, thin, slightly striate and compressed. Leaves all submerged, firm, translucent, linear, usually c. 20-40 mm long and 1-2 mm broad, apex obtuse, with 2 lateral longitudinal veins joining the midrib abruptly near the tip at unequal heights; areas between the lateral and central veins without a distinct lacunar system, sometimes with a narrow dense band of small cells flanking the midrib; stipular sheaths 6-17 mm, tubular, splitting later, usually semi-persistent, pale brown. Spikes axillary, usually shorter than the leaves; scape thin, becoming firm in fruit, 1-4 cm long; flowers 2-4 per whorl with up to 4 whorls per spike. Drupe 2-2.5 mm long and 1-1.5 mm broad, pale olive green, obovoid, smooth, ventral face convex, dorsal more strongly convex, with a faint brown keel when dry, beak short and straight.
6–9. Gräben, flachgründige stehende Gewässer, kollin-subalpin. CH zerstreut.
Dams, ponds and pools which may dry out each year, surviving dry conditions as seed or tubers. Grows from sea level up to ±2740 m.
Fresh water, dams, streams.
Occurs in fresh water.
Dry Grassland; Mesic Grassland. Fresh water, dams, streams.
Europe, Africa, Asia & America: NAM, BOT, LI, NW, GA, MR SW1, FS, KN, LES, NC, WC, EC.
Africa and N hemisphere.
Widespread in the northern hemisphere and Africa. Fairly common in southern Africa.