Jepson eFlora: Taxon page
Vascular Plants of California
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Azolla microphylla

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.
Genus: AzollaView DescriptionDichotomous Key

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.
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
Azolla microphylla Kaulf.
Habit: Plant green or blue-green to dark red. Stem: prostrate, generally 1--1.3 cm; internodes < 1 mm. Leaf: with generally conspicuous papillae on upper leaf lobe. Sporangium Case: male and female, often 0, female with equatorial girdle, wall +- smooth to pitted.
Ecology: Ponds, slow streams; Elevation: < 1200 m. Bioregional Distribution: n&s SNH, GV, CCo, SnFrB, SnBr, SNE; Distribution Outside California: to British Columbia, central United States, South America. Note: Geog +- uncertain due to confusion with Azolla filiculoides.
Synonyms: Azolla mexicana C. Presl
Jepson eFlora Author: Alan R. Smith & Andy Murdock
Reference: Reid et al. 2006 Int J Pl Sci 167:529--538
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Listed on CNPS Rare Plant Inventory

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Citation for this treatment: Alan R. Smith & Andy Murdock 2012, Azolla microphylla, in Jepson Flora Project (eds.) Jepson eFlora,, accessed on October 15, 2019.

Citation for the whole project: Jepson Flora Project (eds.) 2019, Jepson eFlora,, accessed on October 15, 2019.

No expert verified images found for Azolla microphylla.

Geographic subdivisions for Azolla microphylla:
n&s SNH, GV, CCo, SnFrB, SnBr, SNE
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map of distribution 1
(Note: any qualifiers in the taxon distribution description, such as 'northern', 'southern', 'adjacent' etc., are not reflected in the map above, and in some cases indication of a taxon in a subdivision is based on a single collection or author-verified occurence).


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Data provided by the participants of the  Consortium of California Herbaria.
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All markers link to CCH specimen records. The original determination is shown in the popup window.
Blue markers indicate specimens that map to one of the expected Jepson geographic subdivisions (see left map). Purple markers indicate specimens collected from a garden, greenhouse, or other non-wild location.
Yellow markers indicate records that may provide evidence for eFlora range revision or may have georeferencing or identification issues.

CCH collections by month

Duplicates counted once; synonyms included.
Species do not include records of infraspecific taxa, if there are more than 1 infraspecific taxon in CA.
Blue line denotes eFlora flowering time.