Novelo R., A. and A. Lot H. 1994. Potamogetonaceae. Pp. 13-15 in Davidse, G., Sousa, M. and Chater, A. (eds.). Flora Mesoamericana 6: 1-543. Universidad Nacional Autónoma de México: México, D. F.

 

3 genera and ca. 110 spp.; subcosmopolitan, chiefly temperate, extending into tropical regions primarily at higher elevations; 2 genera, 5 spp. in CR.

Perennial or annual aquatic herbs, freshwater and brackish to saline habitats; rooted, often with submersed or submersed and floating leaves. Stems elongate, typically arising from a rhizome, ascending to the surface. Leaves chiefly alternate, decussate, or in some, subopposite, submersed or submersed and floating, stipules present (CR) or absent. Inflorescences spicate, 2-30 flowers. Flowers bisexual. Perianth (2-)4, bract-like, or absent. Stamens 2 or 4, adnate to perianth base. Pistils typically 4 (1-8), ovaries superior. Fruits 1-seeded, drupaceous (remaining fleshy in water) or nutlets.

These aquatic plants are poorly collected because leaves are submerged and flowers and fruits are very small, thus plants may appear sterile. Some species can become very weedy.

1. Inflorescence of 1-several verticils, not hidden by stipules; stamens 4; perianth present; fruits sessile...Potamogeton

1. Inflorescence of 2 flowers, usually hidden by stipular sheath, (peduncle elongating after fertilization); stamens 2; perianth absent; fruits borne on long stalks (podogyne--elongation of base of gynoecium), appearing umbelliform...Ruppia

Ca. 100 spp., chiefly temperate, with several species extending into tropical regions at higher elevations; 4 spp. reported for CR.

Perennial or some annual, freshwater habitats. Plants totally submersed or with submerged and floating leaves; rhizomatous. Submerged leaves sessile, linear, ribbon-like or filiform, or lanceolate to ovate to elliptic to oblong to oblanceolate, margins usually entire, sometimes serrulate, stipules free (CR) or adnate to the leaf base. Turions (winter buds/hybernacula) present or absent. Inflorescence spicate, flowers in 1-several verticils, pedunculate. Flowers 4-merous, sessile. Stamens 4. Pistils 4, sessile. Fruits drupaceous, sessile.

Plants of Potamogeton are little collected. They are often encountered only in vegetative condition and are therefore difficult to identify. Fruits are frequently critical for correct determinations. Most of the species have wide distributions and 2 additional species might be expected in CR, P. nodosus, with long petiolate floating leaves (as well as submerged), and Stuckenia pectinata (Potomogeton pectinatus), a much-branched submersed species with filiform leaves and stipules adnate to the leaf base; no collections of these two species have been seen for CR.

1. Submersed leaves broad, lanceolate to elliptic to oblong-elliptic to oblong to oblanceolate; leaf margins wavy to crisped.

2. Leaf margins serrulate, distinctly crisped, rounded at apex; inflorescence with 3-5 verticils……..P. crispus

2. Leaf margins entire, somewhat wavy, tapering to acute apex; inflorescence with 8-15 verticils....P. illinoensis

1. Submersed leaves linear, ribbon-like; leaf margins flat.

3. Submersed leaves very narrow, 0.4-2.8 mm wide; central band of lacunae narrow, 1/4 or less the width of the leaf, ca. 0.2 mm wide...P. pusillus

3. Submersed leaves less narrow, (1-)1.8-3.5(-4.1) mm wide; central band of lacunae wide, ca. 1/2 the width of the leaf, 1-2.5 mm wide...P. paramoanus

Potamogeton crispus L., Sp. Pl. 126. 1753.

Winter annual, surviving warmer season as bur-like turions. Totally submersed. Leaves oblong to oblanceolate, rounded at apex, margins wavy to crisped, conspicuously serrulate. Inflorescences terminal and axillary, flowers in 3-5 verticils, emergent. Fruits flattened, 2-3.5 mm long, 2-2.5 mm wide, with a dorsal keel; beak elongate, acuminate beak, about as long as the body.

Submersed in ponds, lakes and quiet waters of streams. Valles Río La Estrella and Río Tarcoles [Grayum, Warner & Schatz 5235, CR, MO], fertile April. Introduced from Eurasia, widespread Northeastern North America to Argentina.

This species is often a noxious weed, thriving especially in polluted or calcareous waters.

Potamogeton illinoensis Morong, Bot. Gaz. (Crawfordsville) 5: 50. 1880.

Perennial, turions absent. Totally submersed. Leaves broad, lanceolate to elliptic to oblong-elliptic to oblanceolate, tapering to acute apex, margins somewhat wavy, entire. Inflorescences terminal or axillary, flowers in 8-15 verticils, emergent. Fruits flattened, 2.5-3.5 mm long, 2.1-3 mm wide, with dorsal keel, lateral keels not prominent, but often with a conspicuous knob at base; beak prominent, about 0.5 mm long.

Lakes, ponds and quiet waters of rivers. Cordilleras Tilaran and Central [Crow, Rivera & Charpentier 7461, CR, MO, NHA], specimens sterile. Widespread North America from Canada to Mexico, south to Argentina.

Potamogeton paramoanus Haynes & Holm-Neilsen, Syst. Bot 7: 498. 1982.

Perennial, turions absent. Submersed and floating. Submersed leaves linear, ribbon-like, 3.5-26.5 mm long, 1-4.1 mm wide, with wide lacunae band, ca. 2 mm wide, ca. 1/2 as wide as the leaf. Petiolate floating leaves sometimes present (especially when flowering), subopposite, blades elongate, elliptic to oblong-elliptic, 14-31 mm long, 6-9 mm wide; petioles usually flattened. Inflorescences terminal and in the axils of both submersed and floating leaves, flowers in 6-8 verticils (both submersed and emergent). Fruits plump, dorsally winged, ca. 2.5 mm long, ca. 2.1 mm wide, each side with a lateral keel; beak prominent, 0.5 mm long.

High elevation ponds, lakes and streams, known only from a stream in Cordillera Talamanca, Atlantic Slope [Davidse, Herrera & Grayum 28858, CR, MO]; specimens sterile. CR; Andies, Columbia to Peru.

Potamogeton pusillus L., Sp. Pl. 127. 1753.

Perennial, plants forming turions. Totally submersed. Submersed leaves linear, delicate, ribbon-like, 15-85 mm long, (0.4-)1-2.8 mm wide, with very narrow lacunae band, ca. 0.2 mm wide, ca. 1/4 or less as wide as the leaf. Inflorescences axillary, flowers in 3-5 widely spaced verticils, emergent. Fruits plump, lacking a dorsal keel, 1.7-2(-2.8) mm long, 1-1.5(-1.8) mm wide; beak prominent. ca. 0.5 mm long. Lakes, ponds, quiet waters of streams. Cordillera Central [Crow, Rivera & Charpentier 7464, CR, MO, NHA), fertile Oct. Widespread, Canada to Argentina; Eurasia.

Var. pusillus occurs in CR.

Ca. 10 spp.; subcosmopolitan; 1 sp. reported for CR.

Ruppia maritima L., Sp. Pl. 127. 1753.

Perennial or annual, brackish to saline habitats. Plants totally submersed. Stems elongate, perennial spp. (CR) arising from a rhizome, ascending to the surface. Leaves alternate, or subopposite, filiform, with conspicuous adnate stipule sheathing at the base. Inflorescences of 2 flowers, sessile, usually hidden by stipular sheath at anthesis, peduncle short, elongating and loosely coiled after fertilization. Perianth absent. Stamens 2. Ovaries 4 (CR), separate, sessile. Fruits drupaceous or nutlets, long-stipitate, base of gynoecium greatly enlongating during development of fruit (podogyne), appearing umbelliform.

Coastal ponds, somewhat saline waters. Known only from Pacific Coast, Santa Rosa [Grayum, Sleeper & Machado 5131, CR, MO], fertile Jan. Cosmopolitan.

This species probably occurs more widely in coastal ponds. It often appears sterile, even though fertile, and may easily be overlooked because of its filiform appearance. Underwater pollination has been described in this species. It is often an important food source for waterfowl and cover for fish.