Submerged Hornwort

Scientific name: Ceratophyllum submersum L. 

Family: Ceratophyllaceae

MORPHOLOGY

Habit and dimensions: A perennial herbaceous plant, ranging from 50 cm to 2 m, completely submerged and floating with weak anchorage.

Stems: Tenacious, flexible stems, about 0.5 mm in diameter.

Leaves: Whorled leaves in groups of 4-12, with 3 dichotomies, 10-20 mm long; lower leaves are capillary, while upper ones are up to 1 mm wide, toothed on the outer side.

Flowers: Flowers on axillary peduncles of 2-4 mm, perianth with segments of 5 mm. Blooms from May to September.

Fruits and seeds: Oval fruit of 4 mm without spines.

DISTRIBUTION AND HABITAT

Once common throughout Italy, now rare due to canalization and drainage works and water pollution; absent in Liguria, Piedmont, Aosta Valley, Umbria, Molise, Campania, and Basilicata, and nearly absent in the Po Valley. It grows in stagnant or slowly flowing waters between 0 and 600 m.

Photo: under the free license of Saxifraga and Rutger Barendse, Peter Meininger