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Donald H. Les

Perennial herb, submersed aquatic; overwintering on bottom as detached, dense shoot tips (winter buds); roots 0; monoecious; water-pollinated. Stem: flexible with water currents, internodes clustered near tip. Leaf: whorled, generally compound, forked; segments linear, toothed; stipules 0; petiole 1–2 mm, translucent. Inflorescence: reduced axillary cymes generally near shoot tips, ± sessile, 1–several per node, generally staminate below, pistillate above, or sometimes mixed at a node; flowers 1–3 per cyme but appearing to be 1 subtended by calyx-like whorl of 8–15 bracts, bracts linear, leaf-like, fused at base, toothed at tip, persistent in fruit. Flower: unisexual; perianth 0; staminate round-topped, stamens 3–50, spirally arranged, anthers ± sessile, exserted from bracts, pollen shed underwater; pistillate of 1 simple, ovoid pistil, ovary superior, chamber 1; placenta pendulous; style elongate, spine-like, with decurrent groove; stigma pocket-like, at style base; ovule 1. Fruit: achene, tubercled or not, spines 0 or elongate, basal, facial, marginal or stylar; lateral margin winged or not.
1 genus, 6 species: ± worldwide. [Les 1997 FNANM 3:81–84] —Scientific Editor: Thomas J. Rosatti.

(Greek: horn leaf, for antler-like appearance) Ceratophyllum grown as ornamental or for oxygen generation in aquaria, garden ponds. Leaves, fruit eaten by migrating waterfowl. Vigorous growth (even of native species) can result in weedy infestations.

C. demersum L.
Stem: 1–3+ m, glabrous, limp, suspended by water, brittle, branches 0–3 per node. Leaf: 3–11 per node, 0.8–3 cm; segments 2–4, with 2 rows small teeth distally, 1 multicellular, glandular appendage at tip. Inflorescence: uncommon. Flower: staminate 2–5 mm, stamens pink to ± red; pistillate 1–2 mm, pistil generally ± yellow, margins red-tinged or not, style generally 1 mm. Fruit: 3.5–6 mm (except spines), dark green to red-brown, generally tubercled, base with 2 tubercles or 2 spines, margin spineless, wingless; spines 0.1–12 mm, stiff, bases generally webbed; style persistent on fruit, stiff, erect, 0.5–14 mm. Seed: cotyledons large, fleshy; terminal bud highly developed; first leaves simple, opposite, awl-like.
2n=24,38,40,48. Common. Ditches, lakes, ponds, pools, slow watercourses; water 0.1–4 m deep, fresh to ± brackish, medium to high nutrient levels, acidic to alkaline (pH 5.9–9.4) but generally alkaline (pH > 7); generally < 1700 m. California (except Cascade Range Foothills, Tehachapi Mountain Area, Channel Islands, White and Inyo Mountains, Desert Mountains); common worldwide. [Ceratophyllum apiculatum Cham.] Plants self-fertile; populations generally > 50% staminate. Jun–Aug [Online Interchange]
Unabridged note: Plants with fruit having basal tubercles instead of spines were named Ceratophyllum apiculatum Cham., but such variants occur commonly and sporadically throughout sp. range and do not merit taxonomic recognition.

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Citation for the whole project: Jepson Flora Project (eds.) 2013. Jepson eFlora,, accessed on Nov 29 2015
Citation for this treatment: [Author of taxon treatment] 2013. Ceratophyllum, in Jepson Flora Project (eds.) Jepson eFlora,, accessed on Nov 29 2015

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Geographic subdivisions indicated for the distribution of Ceratophyllum demersum Markers link to CCH specimen records. If the markers are obscured, reload the page [or change window size and reload]. Yellow markers indicate records that may provide evidence for eFlora range revision or may have georeferencing or identification issues.
map of distribution 1
(Note: any qualifiers in the taxon distribution description, such as 'northern', 'southern', 'adjacent' etc., are not reflected in the map above, and in some cases indication of a taxon in a subdivision is based on a single collection or author-verified occurence).

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Data provided by the participants of the Consortium of California Herbaria.
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CCH collections by month

Duplicates counted once; synonyms included.
Species do not include records of infraspecific taxa.
Blue line denotes eFlora flowering time.