spring hornwort (spineless hornwort)
Ceratophyllaceae (Hornwort family)
Introduction to Vascular Plants
Introduction
Spineless hornwort is a perennial floating aquatic species endemic to North America where it is found primarily in the eastern part of the continent and then is disjunct in British Columbia, Washington and Oregon (USDA 2011). In British Columbia, it is found primarily in the southwestern part of the province, in lakes and sloughs in the lowland and montane zones. This species has coarse branching stems and usually no roots. Leaves are forked and arranged in whorls, and are sometimes toothed. Species in this genus are distinctively stiff to touch, and retain their shape when pulled from the water--aiding in identification of the genus.
In writing about the rare plants of the Fraser Valley, Lomer (2011) says: "An aquatic plant much like the common C. demersum, but more slender. It tends to grow in clearer, more acidic bog water than the latter species. [In the Fraser Valley], it has been found at Devil's Lake, west of Hope (Ceska 1978, unpublished), and I expect that further collecting will prove that this species is not rare in southwest BC, though there appear to be very few sites in the Fraser Valley." A complete species description is given in Flora North America. |
Species Information
General:
Aquatic herb, usually without roots; stems freely branching, 0.3-4.0 m long.
Leaves:
Stem leaves submerged, in whorls of 5-12, 2-4 times forked into linear or threadlike segments, these usually entire or sometimes finely toothed.
Flowers:
Inflorescence of solitary, minute, axillary flowers; petals lacking; sepals 3-15, sometimes petal-like; stamens 12-16.
Fruits:
Achenes usually lacking, if present then much flattened, 5-7 mm long, ellipsoid, wing-margined with several lateral spines.
Illustration
If more than one illustration is available for a species (e.g., separate illustrations were provided for two subspecies) then links to the separate images will be provided below. Note that individual subspecies or varietal illustrations are not always available.
Illustration Source: The Illustrated Flora of British Columbia
Habitat and Range
Lakes and sloughs in the lowland and montane zones; locally frequent on S Vancouver Island and the Gulf Islands, rare in the lower Fraser Valley and along the Alaska Highway; E to MI and ME and S to FL and MX.Status Information
Synonyms
Synonyms and Alternate Names:
Ceratophyllum demersum var. echinatum (A. Gray) A. Gray
Ceratophyllum submersum var. echinatum (A. Gray) Wilmot-Dear
Taxonomic Keys
TAXONOMIC KEY TO CERATOPHYLLUM
1. Fruits wing-margined, with several lateral spines; leaf divisions fine, threadlike, sometimes with fine teeth C. echinatum 1. Fruits wingless, with only two basal spines; leaf divisions stout, stiff, with distinct teeth C. demersum |
Taxonomic Notes
This species is cold-water tolerant and is reported to overwinter under ice. It is often grown in aquatic gardens.
|