Isoetes (Hickey, 1984)

Kessler, Michael & Smith, Alan R., 2018, Prodromus of a fern flora for Bolivia. IV. Isoëtaceae, Phytotaxa 344 (1), pp. 83-86 : 84

Key to the Bolivian species of Isoëtes

1 Plants of eastern lowlands <500 m; leaves 15–75 cm long ......................................................................................... I. panamensis

– Plants of Andean habitats 2500–5200 m; leaves 3–25 cm long ....................................................................................................... 2

2 Rootstocks vertically elongate; leaves 50–200 per rootstock, 3–5(7.5) cm long; plants of cushion bogs ....................... I. andicola

– Rootstocks globose; leaves <40 per rootstock, 4–25 cm long; plants of lakes, pools, streams, and marshes .................................. 3

3 Leaves turgid, stiffly erect; velum covering (20)70–100% of each sporangium ............................................................................. 4

– Leaves flaccid, lax to weakly erect; velum covering 0–80(100)% of each sporangium .................................................................. 5

4 Leaves to 20 per rootstock, 4–9 cm long, green, basally without dark pigmentation; rootstocks globose to slightly horizontally elongate; megaspores usually rugulate, rarely smooth ...................................................................................................... I. herzogii

– Leaves to 40 per rootstock, 9–16 cm long, dark green, usually basally with dark brown to nearly sclerotic pigmentation; rootstocks globose to extensively horizontally elongate; megaspores smooth .................................................................................... I. lechleri

5 Velum covering (5)60–80(100)% of each sporangium; gemmae absent; megaspores smooth to minutely tuberculate or cristate; microspores verrucate .................................................................................................................................................... I. boliviensis

– Velum covering 0–10(40)% of each sporangium; gemmae present at leaf bases; megaspores tuberculate, rarely almost smooth or rugulate; microspores echinate ..................................................................................................................................... I. eshbaughii