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W. Carl Taylor & Jon E. Keeley

Perennial herb, aquatic to terrestrial. Stem: buried, corm-like, 2–3-lobed, corky, brown. Leaf: simple, in grass-like tufts, spirally arranged on stem top, erect to spreading, < 30 cm, linear above base. Sporangium: solitary, embedded in wide leaf base, < 1 cm, ± covered by a translucent membrane, male or female; male spores > 10000, < 0.045 mm, ± bean-shaped, gray or brown in mass; female spores 20–200, 0.2–0.7 mm, spheric, white, ± smooth, ridged, tubercled, or prickly.
1 genus, 200+ species: worldwide. [Taylor et al. 1993 FNANM 2:64–75] —Scientific Editors: Alan R. Smith, Thomas J. Rosatti.
Unabridged references: [Pfeiffer 1922 Ann Missouri Bot Gard 9:79–233]

(Greek: evergreen, from habit of some species) Perhaps most poorly known lycophyte genus. Mature female spores, found in decaying leaf bases or soil, critical for identification, as are hand lens for texture when dry, microscope with micrometer for size. Hybrids (spores of variable size, shape) common between aquatic species, making them less distinct.

Key to Isoetes

I. occidentalis L.F. Hend.
Plant underwater. Leaf: evergreen, < 20 cm, rigid, brittle, tapered to tip, dark green; base brown-white. Sporangium: membrane covering < 50%; male spores 0.035–0.045 mm, gray in mass; female spores 0.5–0.7 mm, ridged, tubercled.
2n=66. Persistent lakes, pools; > 1500 m. Klamath Ranges, High Sierra Nevada; to British Columbia, Colorado. [Isoetes lacustris var. paupercula Engelm.] Hybridizes with Isoetes bolanderi, Isoetes echinospora. Spores mature late summer. [Online Interchange]

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Citation for the whole project: Jepson Flora Project (eds.) 2013. Jepson eFlora,, accessed on Dec 1 2015
Citation for this treatment: [Author of taxon treatment] 2013. Isoetes, in Jepson Flora Project (eds.) Jepson eFlora,, accessed on Dec 1 2015

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Geographic subdivisions indicated for the distribution of Isoetes occidentalis Markers link to CCH specimen records. If the markers are obscured, reload the page [or change window size and reload]. Yellow markers indicate records that may provide evidence for eFlora range revision or may have georeferencing or identification issues.
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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CCH collections by month

Duplicates counted once; synonyms included.
Species do not include records of infraspecific taxa.
Blue line denotes eFlora flowering time.