Jepson eFlora: Taxon page
Vascular Plants of California
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Isoetes howellii

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. Sporangia: 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.
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 howellii Engelm.
Habit: Plant becoming terrestrial. Leaf: deciduous, < 30 cm, rigid, not brittle, tapered to tip, bright green; base +- brown to black. Sporangia: membrane covering < 75%; male spores 0.025--0.035 mm, brown in mass; female spores 0.3--0.5 mm, ridged. Chromosomes: 2n=22.
Ecology: Vernal pools, lake margins; Elevation: generally < 1500(2900) m. Bioregional Distribution: KR, NCoR, CaR, SNF, n SNH, GV, CCo, SnFrB, SCoR, SCo, PR; Distribution Outside California: to Washington, Montana, Utah. Note: Small plants of SCo, Washington, Baja California (leaf < 10 cm, female spore < 0.42 mm) are assignable to Isoetes howellii var. minima (A.A. Eaton) N. Pfeiff., recognition of which remains questionable pending further research, although it is +- clear that it should not be treated as an infraspecific taxon of Isoetes howellii. Spores mature late spring, summer.
Jepson eFlora Author: W. Carl Taylor & Jon E. Keeley
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Botanical illustration including Isoetes howellii

botanical illustration including Isoetes howellii


Citation for this treatment: W. Carl Taylor & Jon E. Keeley 2012, Isoetes howellii, in Jepson Flora Project (eds.) Jepson eFlora,, accessed on February 23, 2019.

Citation for the whole project: Jepson Flora Project (eds.) 2019, Jepson eFlora,, accessed on February 23, 2019.

Isoetes howellii
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© 2004 Carol W. Witham
Isoetes howellii
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© 2007 Neal Kramer
Isoetes howellii
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© 2007 Neal Kramer
Isoetes howellii
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© 2013 Vernon Smith

More photos of Isoetes howellii in CalPhotos

Geographic subdivisions for Isoetes howellii:
KR, NCoR, CaR, SNF, n SNH, GV, CCo, SnFrB, SCoR, SCo, PR;
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, if there are more than 1 infraspecific taxon in CA.
Blue line denotes eFlora flowering time.