Jepson Herbarium
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Perennial, [ shrub, vine], terrestrial [growing on other plants or not], or aquatic, sometimes free-floating, then sometimes much reduced, in dense, clonal populations, 0.4–10 mm, flat and tongue-shaped to spheric, not differentiated into stems and leaves, new plants produced in budding pouch at base or along margins, sometimes overwintering on bottom as dense, rootless, starch-filled daughter plant (winter bud); often from short, generally erect caudex; roots 0–many; often monoecious.
Stem: sometimes above ground in addition to caudex, or not differentiated from plant body.
Leaf: simple or compound, basal (or cauline, 2-ranked), or not differentiated from plant body.
Inflorescence: generally spike, fleshy, generally ill-smelling, or flower 1, rarely seen, minute, appearing like 2–3 unisexual flowers, often sheathed by minute membrane; flowers bisexual or pistillate below, staminate above; bract subtending spike 1, generally showy ( petal-like), generally > spike, sheathing or not.
Flower: perianth parts 0, 4, 6, free or fused; stamens 0–4, 6, free or fused; ovary superior to 1/2-inferior and sunken in inflorescence axis, chambers 1–3, stigma ± sessile.
Fruit: berry or achene-like, winged or not.
Seed: 1–many, often ribbed.
± 114 genera, 1850 species: generally tropics, subtrop; some cultivated for food, ornamental in ponds, aquaria (Colocasia, taro) or ornamental (Philodendron, Anthurium). [Les et al. 2002 Syst Bot 27:221–240; Thompson 2000 FNANM 22:128–142] Since TJM (1993), including Lemnaceae, and except Acorus, now in Acoraceae (the sole member in CA, Acorus calamus L., is an historical waif). Pistia stratiotes L. {Noxious weed} is a waif. Pinellia ternata (Thunb.) Breitenbach possibly naturalized in CA. In taxa once included in Lemnaceae, vein number per plant body best determined using backlight. —Scientific Editors: Bruce G. Baldwin, Thomas J. Rosatti.
Unabridged references: [Armstrong, http://waynesword.palomar.edu/1wayindx.htm; Stockey et al. 1997 Amer J Bot 84:355–368; Les et al. 2002 Syst Bot 27(2):221–240]
Unabridged note: Since TJM (1993), incl Lemnaceae, except Acorus, now in Acoraceae (the sole representative of the family in CA, Acorus calamus, judged to be an historical waif in CA and therefore here except). Incl smallest of all known angiosperms (Wolffia globosa) as well as world's most massive inflorescence (spike of Amorphophallus titanum, Titan Arum, to 4 m in circumference). Needle-like crystals in most tissues cause intense irritation when chewed; those of Dieffenbachia, dumb-cane, may induce temporary speechlessness. Incl of fossil evidence in cladistic analyses indicate Lemnaceae and Pistia form a monophyletic group within Araceae (Stockey et al.), a position now generally accepted (see Les et al.). Pinellia ternata (Thunb.) Makino ex Breitenbach introduced, possibly naturalized in CA. Taxa formerly incl in Lemnaceae may be very invasive. In taxa formerly incl in Lemnaceae, vein number per plant body best determined using backlight. Peltandra virginica (L.) Schott & Endl., incl in TJM (1993), reportedly spread from ornamental pool introduction in 1970 to nearby reserviors, but degree of reproduction or even persistence there unknown.

Key to Araceae

Plants much reduced, not differentiated into stems, leaves; floating aquatics; roots 0.
Plant body: generally in unequal 2s; 0.4–1.3 mm, ± cylindric to nearly spheric, floating on or partially below water surface; veins 0; budding pouch funnel-shaped; winter buds often produced.
Flower: produced in cavity on upper surface; sheathing membrane 0; stamen 1; pistil 1.
Seed: smooth.
11 species: worldwide, especially temperate, tropics. (J.F. Wolff, German botanist, physician, 1778–1806) [Armstrong & Thorne 1984 Madroño 31:172–179] Key for use at > 10×.

Plant body: 0.8–1.3 mm, nearly spheric, basally transparent, upper surface flat, dark green, only center floating above water, stomates generally 15–100.
Uncommon. Freshwater; < 200 m. South Coast (San Diego Co.);

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Citation for the whole project: Jepson Flora Project (eds.) [year] Jepson eFlora, http://ucjeps.berkeley.edu/IJM.html [accessed on month, day, year]
Citation for an individual treatment: [Author of taxon treatment] [year]. [Taxon name] in Jepson Flora Project (eds.) Jepson eFlora, [URL for treatment]. Accessed on [month, day, year].

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Bioregions in which taxon occurs	Red area (if present) is the part of the bioregion lying between the upper and lower elevation limits of the taxon; 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 have georeferencing or identification issues.
Chart based on elevation range in Manual and elevations and coordinates of CCH records. Data provided by the participants of the Consortium of California Herbaria. Note: About half of the CCH records include both elevation and coordinates.	Map made in collaboration with Scott Loarie. Data provided by the participants of the Consortium of California Herbaria. View all CCH records   CCH collections by month Duplicates counted once; synonyms included. Species do not include records of infraspecific taxa. Blue line denotes Manual flowering time.