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Key to families | Table of families and genera

Specimen numbers are hyperlinked to records in the Consortium of California Herbaria data view where possible. Taxa are hyperlinked to entries in the Jepson Interchange via the "[Online Interchange]" link.

 

WOLFFIA WATERMEAL

Wayne P. Armstrong


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×.

Key to Wolffia

1. Tip of plant body acute, upper surface ± concave or flat — dead plant with brown cells ..... W. borealis

1' Tip of plant body rounded, upper surface ± convex (except Wolffia arrhiza)

2. Upper surface of vegetative plant body with a conical bump near center; dead plant with brown cells ..... W. brasiliensis

2' Upper surface of plant body smooth; dead plants without brown cells

3. Upper surface dark green, flat; stomates generally 15–100 ..... W. arrhiza

3' Upper surface transparent green, ± convex; stomates 1–10(30)

4. Plant body 0.8–1.3 mm, ± spheric, upper surface mostly convex, center flat ..... W. columbiana

4' Plant body 0.4–0.8 mm, longer than wide, upper surface barely convex throughout ..... W. globosa

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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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