Photographs: The Gearagh, Co. Cork

Rigid Hornwort Ceratophyllum demersum Cornlach Family: Ceratophyllaceae Flowering June-July. Submerged aquatic perennial. Native. Minute monoecious flowers are stalkless and auxillary but the smooth or slightly warty fruit is rarely produced. Branched stems with numerous whorls of 6-8 rigid, dark-green leaves. Leaves are 1-2 times forked, the segments fine-toothed. Stems to 1m. Rare, very local distribution in Ireland in still or slow-moving lakes, ponds and canals. Identified by Paul Green Similar: Spiked Water-milfoil, Myriophyllum spicatum

Rigid Hornwort, Ceratophyllum demersum, Cornlach