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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.



Richard V. Lansdown & Robert E. Preston

Annual [perennial herb], in water or on wet ground; monoecious [dioecious]. Stem: slender, generally ascending under water, floating on surface, or prostrate on ground, generally much-branched. Leaf: generally opposite, 4-ranked, lance-linear to spoon-shaped, entire [lobed]. Inflorescence: flowers 1–2(4) per leaf axil, bracts 2, ± white, generally inflated, or 0. Flower: minute, unisexual; perianth 0. Staminate flower: stamen 1, filament elongate. Pistillate flower: ovary superior, slightly lobed at tip and base, chambers 4, styles 2, thread-like. Fruit: 0.6–1.6[2.4] mm, ± dry, ± grooved lengthwise, splitting into 4 achene-like units.
± 75 species: tropics, temperate. (Greek: beautiful hair, from long linear submerged leaves of some of Medit taxa) [Lansdown 2009 Novon 19:364–369] Taxonomically difficult; mature fruit and 10× magnification needed for identification. Callitriche peploides Nutt. a nursery weed in southern California; Callitriche stenocarpa Hegelm., misappl. to various California taxa, but recorded from many sites in the Rocky Mountains and could be expected in California.
Unabridged references: [Fassett 1951 Rhodora 53:137–155, 161–182, 185–194, 209–222; Philbrick & Jansen 1991 Syst Bot 16:478–491; Philbrick & Les 2000 Aq Bot 68:123–141]

Key to Callitriche

1. Leaf dark green, contrasting strongly with pale stem; leaves all ± linear or tapering from near base; no leaves with > 1 central vein ..... C. fassettii

1' Leaf pale green and not contrasting strongly with stem; leaves ± linear and vein 1, to broad, petioled, and veins > 1

2. Fruit wing 0 or winged only distal to middle

3. Fruit length >= width, wing distal to middle only or 0; fruit with evident lines of cells on faces ..... C. palustris

3' Fruit length ± = width, generally wing 0; cells on fruit faces obscure ..... C. heterophylla

4. Fruit 0.8–1.4 mm ..... var. bolanderi

4' Fruit 0.6–0.8 mm ..... var. heterophylla

2' Fruit winged from tip to base

5. Peduncle in fruit 2–25 mm

6. Fruit length >= width, 1–1.2 mm, 0.9–1.2 mm wide ..... C. longipedunculata

6' Fruit length < width, 0.7–1 mm, 1.1–1.4 mm wide ..... C. marginata (2)

5' Peduncle in fruit 0–1 mm

7. Mature fruit gray-brown, not contrasting strongly with wing ..... C. stagnalis

7' Mature fruit dark brown to black, contrasting strongly with translucent wing

8. Fruit length < width, 0.7–1 mm, 1.1–1.4 mm wide ..... C. marginata (2)

8' Fruit length = width, 1–1.5 mm, 1–1.5 mm wide ..... C. trochlearis


Citation for the whole project: Jepson Flora Project (eds.) [year] Jepson eFlora, [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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