hornwort

Short definition from Wiktionary

Noun

1. 1
   A bryophyte, of phylum Anthocerotophyta, with a leafless thallus characterized by a dominant gametophyte stage of the life cycle and a sporophyte stage shaped like a horn.
2. 2
   An aquatic flowering plant in the genus Ceratophyllum
3. 3
   Vernal grasses (Anthoxanthum spp.).