Araceae
Spirodela polyrrhiza (L.) Schleid.
SUMMARY
Fronds rounded or pointed at the tip, 1.5-10 mm long, 1.5-8.0 mm wide, 1-1 1/2 times as long as wide, thin or (rarely) gibbous, sometimes with a red spot above the node; nerves 40-70 urn wide; air spaces in 2-4 layers, nearly reaching the margin; roots 7-21, 1 or (rarely) 2 of which perforate the prophylluin; rootcap rounded or pointed on living specimens, always pointed on dried specimens; small, orbicular to reniform shaped, brownish to olive turions without roots present which form under unfavourable conditions and sink to the bottom of the water. INFLORESCENCE/INFRUCTESCENCE: Plants very rarely flowering and fruiting. Ovary with 1-2 ovules (MAHESHWARI and MAHESHWARI 1963 rarely counted up to 4 ovules; but the material of these authors originated from a botanical garden and may have consisted of S. intermedia ). Style about 0.3 mm long; fruit 1.0-1.5 mm long and 1.0-1.5 mm wide; winged edges of the fruit near the top about 0.15 mm wide; seeds 1 (rarely 2), 0.7-1.0 mm long, about 0.7 mm thick, with 12-20 distinct ribs; external seed coat with 8-11 subepidermal cell layers.