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Jepson Interchange (more information)
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AZOLLACEAE

MOSQUITO FERN FAMILY

Alan R. Smith

Plant free-floating or stranded on mud, generally 1–5 cm, often fan-shaped; roots pendent from stem forks, unbranched
Stem forked repeatedly or pinnate, thread-like, easily fragmented at joints
Leaves alternate, in 2 rows, sessile, often overlapped, 0.5–1.5 mm, seemingly paired but actually of 2 roundish to ovate lobes; upper lobe floating or emergent, thick, greenish or reddish, margin whitish; lower lobe submersed, generally slightly larger, thinner, whitish
Sporangia in seemingly axillary cases of 2 kinds, cases generally in pairs of 1 kind
Male sporangium case 1.2–2 mm diam, spheric; tip dark-pointed; wall transparent; sporangia generally 20–100+, long-stalked; spores 32 or 64, spheric, in generally 3–6 barbed masses
Female sporangium case 0.2–0.4 mm diam, hemispheric or spheric; tip obtuse, covered by dark, conic, spongy structures that aid in flotation; wall ± opaque; sporangium 1, sessile; spore 1, spheric
Genera in family: 1 genus, ± 7 species: ± worldwide. Salvinia molesta D.S. Mitch. has been tentatively identified from Walter's Camp, Imperial Co.; more study needed.

AZOLLA


Etymology: (Greek: dry kill, from plant death in dried habitats)
Reference: [Perkins et al. 1985 Scanning Electron Microscopy 1985(IV):1719–1734]
Used as green manure in rice paddies because of nitrogen-fixing algae in upper leaf lobe; species identification requires generally female sporangium cases (generally 0 on herbarium specimens), often leaf sectioning, compound microscope.

Native

A. mexicana C. Presl

MEXICAN MOSQUITO FERN

Plant green or blue-green to dark red or red-fringed, generally fertile
Stems prostrate, generally 1–2 cm; internodes < 1 mm
Sporangium cases often male and female
Ecology: UNCOMMON. Habitats of A. filiculoides
Elevation: ± 100 m.
Bioregional distribution: Sacramento Valley, possibly n Sierra Nevada
Distribution outside California: to British Columbia, c US, S.America
Horticultural information: still water [not saline] or mud: 4, 5, 6, 7, 8, 9, 10, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24.
See the CNPS Inventory for information about endangerment and rarity.
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