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Vascular Plants of California
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Higher Taxonomy
Family: AzollaceaeView Description 

Habit: 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. Leaf: alternate, in 2 rows, sessile, often overlapped, 0.5--1.5 mm, seemingly paired but actually of 2 +- round to ovate lobes; upper lobe floating or emergent, thick, +- green or +- red, margin +- white, adaxial surface smooth or generally with papillae; lower lobe submersed, generally +- larger, thinner, +- white. 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, +- 6 species: +- worldwide. Note: When Salvinia and Azolla in same family, the name is Salviniaceae.
Unabridged Note: Barbs evidently on neither sporangia nor spores, but on cells surrounding spore masses. If Salvinia is included in the same family with Azolla, as is sometimes done, the name for the inclusive family would be Salviniaceae.
eFlora Treatment Author: Alan R. Smith & Andy Murdock
Scientific Editor: Thomas J. Rosatti.

Etymology: (Greek: dry kill, from plant death in dried habitats) Note: Used as green manure in rice paddies because of nitrogen-fixing algae in upper leaf lobe; species identification difficult, depends in part on fertile material (generally 0 on herbarium specimens). Species hybridize in culture.
Unabridged Note: Evard & Van Hove (2004) treated Azolla microphylla as a synonym of Azolla filiculoides, suggesting that plants here called Azolla microphylla might instead belong to Azolla cristata Kaulf., although no California material was referred to this sp. by them.
Jepson eFlora Author: Alan R. Smith & Andy Murdock
Reference: Reid et al. 2006 Int J Pl Sci 167:529--538
Unabridged Reference: Perkins et al. 1985 Scanning Electron Microscopy 1985(IV):1719--1734; Evard & Van Hove 2004 Syst. Geogr. Pl. 74:301--318
Index of California Plant Names (ICPN; linked via the Jepson Online Interchange)
Key to Azolla

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Next taxon: Azolla filiculoides

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Citation for this treatment: Alan R. Smith & Andy Murdock 2012, Azolla, in Jepson Flora Project (eds.) Jepson eFlora, /eflora/eflora_display.php?tid=10288, accessed on February 22, 2020.

Citation for the whole project: Jepson Flora Project (eds.) 2020, Jepson eFlora,, accessed on February 22, 2020.