PLANT: Submerged aquatics. LEAVES: 4.5–19(–24) cm long, usually somewhat stiff but flexible, tapered abruptly to the sharply pointed tip. SPORANGIA: 4–12 mm long, ellipsoid, the wall often with fine brown-streaks. VELUM: covering less than 1/2 of the sporangium. MEGASPORES: 0.3–0.5 mm in diameter, white, rugulose or tuberculate. MICROSPORES: 20–30 μm long, grayish brown, spinulose. 2N = 22. NOTES: Ponds and lakes (Fig. 3): Apache, Cochise, and Coconino cos. (Fig. 1); 1900–2700 m (6000–8900 ft); Jul–Sep; WA to MT, s to CA, WY, and NM; w Can. This species is quite uncommon in Arizona. Populations in a few ponds along the Mogollon Rim in Coconino County have not been seen in recent decades due to the lowering of the local water table, but the spores are long-lived and the species may reappear if conditions change. Plants in the Lukachukai Mountains of Apache County still appear relatively secure. The single historical specimen from the Huachuca Mountains originally was referred to var. pygmaea (Englem.) Clute, a small-leaved form not recognized by most current botanists. It has not been relocated in Cochise County in modern times. REFERENCES: Windham, M. D. and G. Ytskievych. 2009. Vascular Plants of Arizona: Isoëtaceae. CANOTIA 5 (1): 27–29.