Jepson Flora Project: Jepson Interchange    

link to manual TREATMENT FROM THE JEPSON MANUAL (1993) previous taxon | next taxon
Jepson Interchange (more information)
©Copyright 1993 by the Regents of the University of California

  • Up-to-date information about California vascular plants is available from the Jepson eFlora.



W. Carl Taylor and Jon E. Keeley

Perennial, aquatic to terrestrial
Stem buried, corm-like, 2–3-lobed, corky, brown
Leaves simple, in grass-like tufts, spirally arranged on stem top, erect to spreading, < 25 cm, linear above base
Sporangia solitary, embedded in wide leaf base, < 1 cm, ± covered by a translucent membrane, either male or female; male spores > 10,000, < 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, 150 species: worldwide
Reference: [Pfeiffer 1922 Ann Missouri Bot Gard 9:79–233]



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


I. howellii Engelm.

Plant becoming terrestrial
Leaves deciduous, < 30 cm, rigid, not brittle, gradually tapered to tip, bright green; bases brownish to black
Sporangium: membrane covering < 75%; male spores 0.025–0.035 mm, brown in mass; female spores 0.3–0.5 mm diam, ridged
Chromosomes: 2n=22
Ecology: Vernal pools, lake margins
Elevation: generally < 1500 m.
Bioregional distribution: Klamath Ranges, North Coast Ranges, Cascade Range, Sierra Nevada Foothills, Great Central Valley, San Francisco Bay Area, South Coast Ranges, South Coast, Peninsular Ranges
Distribution outside California: to Washington, Montana, Utah
Spores mature late spring, summer. Small plants of SCo, WA, Baja CA (leaf < 10 cm, female spore < 0.42 mm) have been called var. minima (A.A. Eaton) Pfeiffer.

previous taxon | next taxon
bioregional map for ISOETES%20howellii being generated

Retrieve Jepson Interchange Index to Plant Names entry for Isoetes howellii
Retrieve dichotomous key for Isoetes
Overlay Consortium of California Herbaria specimen data by county on this map
Show other taxa with the same California distribution | Read about bioregions | Get lists of plants in a bioregion
Return to the Jepson Interchange main page
Return to treatment index page

University & Jepson Herbaria Home Page |
General Information | University Herbarium | Jepson Herbarium |
Visiting the Herbaria | On-line Resources | Research |
Education | Related Sites
Copyright © by the Regents of the University of California