ISOETACEAE

QUILLWORT FAMILY

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]

ISOETES

QUILLWORT

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.

Native

I. nuttallii Engelm.

Plant terrestrial
Leaves deciduous, generally > 8 cm, > 1 mm wide at middle, rigid, almost brittle, gradually tapered to tip, light green to gray-green; bases white to brownish, outermost sterile, often surrounded by several black scales
Sporangium: membrane covering > 75%; male spores 0.02–0.03 mm, brown in mass; female spores 0.35–0.6 mm diam, ± shiny, ± tubercled
Chromosomes: 2n=22
Ecology: Seasonally wet soil, temporary streams
Elevation: generally < 1500 m.
Bioregional distribution: North Coast Ranges, Cascade Range Foothills, Sierra Nevada, n San Joaquin Valley, San Francisco Bay Area, Outer South Coast Ranges, South Coast, Peninsular Ranges
Distribution outside California: to British Columbia
Spores mature late spring, summer.