Isoetes howellii Engelm.
Descripción
Rootstock bilobed; leaves ca. 20, ca. 25 cm long, pale to sclerified lustrous black toward bases, half-terete in mid-length transection; velum covering less than 50% of each sporangium; sporangial walls brown-streaked to completely brown; megaspores white, average 375–450 µm in diam., rugate with girdle smooth; microspores brown in mass, average 25–35 µm long, echinate; 2n=22 (USA).A
Forma de vida
TerrestreA
Ejemplar revisado
BCS (Brandegee s.n., 24 Jan 1890, NY, s.n., Nov. 1902, UC; Breedlove & Axelrod 43344, CAS; Carter et al. 2358, UC).
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Elevación
1000 – 1500 mA
Ecología y Hábitat
Temporary pools and streams in seasonally wet, open woodlands. November–January.A
Categoría IUCN
Preocupación menor (LC)B
Categoría NOM-059-SEMARNAT-2010
No incluidaC
Discusión taxonómica
Isoëtes howellii reaches the southern extent of its range in the Sierra La Laguna region of southern Baja California. In this region I. howellii has megaspores with an obscure rugate texture of low, meandering ridges and microspores averaging less than 35 µm in length. Isoëtes montezumae, which generally resembles I. howellii, has tuberculate megaspores, and microspores averaging more than 35 µm in length.A