Myriophyllum L.

Tutin, T. G., Heywood, V. H., Burges, N. A., Moore, D. M., Valentine, D. H., Walters, S. M. & Webb, D. A., 1981, Flora Europaea. Volume 2. Rosaceae to Umbelliferae, Cambridge University Press : 311-312

2. Myriophyllum L. 2

Glabrous, rhizomatous, aquatic perennial herbs. Leaves (in European species) in whorls of 3-6, usually pinnatisect with capillary segments. Inflorescence an emergent spike; flowers mostly unisexual, male above, female below. Sepals 0 or 4, inconspicuous. Petals 0 or 4, caducous in male, inconspicuous or

absent in female flowers. Stamens 4 or 8. Ovary 4-locular; stigmas 4, sessile or subsessile. Fruit separating longitudinally into 4 1-seeded nutlets. 1 Upper bracts pinnatisect, with capillary segments

2 Emergent leaves sparsely glandular; hermaphrodite flowers usually present; fruit smooth 1. verticillatum 2 Emergent leaves densely glandular; hermaphrodite flowers absent; fruit finely tuberculate 4. brasiliense 1 Upper bracts simple, entire or serrate

3 Stamens 4; bracts longer than flowers 5. heterophyllum 3 Stamens 8; bracts shorter than flowers

4 Flowering spike usually more than 4 cm; all flowers whorled

2. spicatum 4 Flowering spike not more than 3 cm; upper flowers solitary or opposite 3. alterniflorum