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ISOETACEAE QUILLWORT FAMILY

W. Carl Taylor & Jon E. Keeley

Perennial, 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]

ISOETES QUILLWORT
(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. howellii Engelm.
NATIVE
Plant becoming terrestrial.
Leaf: deciduous, < 30 cm, rigid, not brittle, tapered to tip, bright green; base ± brown to black.
Sporangium: membrane covering < 75%; male spores 0.025–0.035 mm, brown in mass; female spores 0.3–0.5 mm, ridged.
2n=22. Vernal pools, lake margins; generally < 1500 m. Klamath Ranges, North Coast Ranges, Cascade Range, Sierra Nevada Foothills, Great Central Valley, San Francisco Bay Area, South Coast Ranges, South Coast, Peninsular Ranges; to Washington, Montana, Utah. Small plants of SCo, WA, Baja CA (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. [Online Interchange]
Unabridged note: There are Consortium records that, if verified, would voucher elevations up to 2900 m. The following (and possibly other) accessions, if verified, would represent range extensions (as indicated): CHSC92169, JEPS107682, CHSC24424, CHSC32078, CHSC59069, CHSC69407, JEPS94945, CHSC82704 (n SNH); UCR51945 (c SNH); UCR113019 (Wrn).

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Citation for the whole project: Jepson Flora Project (eds.) [year] Jepson eFlora, http://ucjeps.berkeley.edu/IJM.html [accessed on month, day, year]
Citation for an individual treatment: [Author of taxon treatment] [year]. [Taxon name] in Jepson Flora Project (eds.) Jepson eFlora, [URL for treatment]. Accessed on [month, day, year].

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Bioregions in which taxon occursRed area (if present) is the part of the bioregion lying between the upper and lower elevation limits of the taxon;
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 have georeferencing or identification issues.
map of distribution 1

Chart based on elevation range in Manual and elevations and coordinates of CCH records.
Data provided by the participants of the Consortium of California Herbaria.
Note: About half of the CCH records include both elevation and coordinates.
Map made in collaboration with Scott Loarie. 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 Manual flowering time.