Jepson eFlora: Taxon page
Key to families | Table of families and genera
Previous taxon Index to accepted names and synonyms:
| A | B | C | D | E | F | G | H | I | J | K | L | M | N | O | P | Q | R | S | T | U | V | W | X | Y | Z |
Next taxon
Isoetes occidentalis

Higher Taxonomy
Family: IsoetaceaeView Description 

Habit: 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.
Genera In Family: 1 genus, 200+ species: worldwide.
eFlora Treatment Author: W. Carl Taylor & Jon E. Keeley
Scientific Editor: Alan R. Smith, Thomas J. Rosatti.
Genus: IsoetesView DescriptionDichotomous Key

Common Name: QUILLWORT

Etymology: (Greek: evergreen, from habit of some species) Note: 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.

Isoetes occidentalis L.F. Hend.
Habit: Plant underwater. Leaf: evergreen, < 20 cm, rigid, brittle, tapered to tip, dark green; base brown-white. Chromosomes: 2n=66.
Ecology: Persistent lakes, pools; Elevation: > 1500 m. Bioregional Distribution: KR, SNH; Distribution Outside California: to British Columbia, Colorado. Note: Hybridizes with Isoetes bolanderi, Isoetes echinospora. Spores mature late summer.
Synonyms: Isoetes lacustris var. paupercula Engelm.
eFlora Treatment Author: W. Carl Taylor & Jon E. Keeley
Jepson Online Interchange

Previous taxon: Isoetes nuttallii
Next taxon: Isoetes orcuttii

Name Search
botanical illustration including Isoetes occidentalis


Citation for this treatment: W. Carl Taylor & Jon E. Keeley 2017. Isoetes occidentalis, in Jepson Flora Project (eds.) Jepson eFlora,, accessed on April 25, 2017.

Citation for the whole project: Jepson Flora Project (eds.) 2017. Jepson eFlora,, accessed on April 25, 2017.

Geographic subdivisions for Isoetes occidentalis:
Markers link to CCH specimen records. Yellow markers indicate records that may provide evidence for eFlora range revision or may have georeferencing or identification issues. Purple markers indicate specimens collected from a garden, greenhouse, or other non-wild location.
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).

View elevation by latitude chart
Data provided by the participants of the Consortium of California Herbaria.
View all CCH records

CCH collections by month

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