ABSTRACT
Stems of M. aquaticum are up to around 2m in length, and 4-5mm in diameter near the base. Emerged stems can extend up to 0.4m above the water surface (Figure 9.1). Adventitious roots are usually produced on the lower stem nodes, but creeping plants commonly root from nodes along the entire shoot. Leaves are in whorls of (4-)5-6, and there is a slight dimorphism between the submerged and emerged leaves. The submerged leaves are oblanceolate in outline, rounded at the apex and (17-)35-40mm long and (4-)8-12mm wide, pectinate with 25-30 linear and up to 7mm long pinnae. Emerged leaves are glaucous, erect near the apex, narrowly oblanceolate in outline, rounded at the apex and (15-)25-35mm long and (4-)7-8mm wide with (18-)24-36 pinnae, with a petiole approximately one fifth of the leaf length. The pinnae are linearsubulate, 4.5-5.5mm long, 0.3mm wide with very shortly apiculate tips (Orchard, 1979, 1981, 1985).
