An Illustrated Flora of the Northern United States, Canada and the British Possessions/Isoetaceae

Leaves without peripheral bast bundles. Leaves without stomata; plants submerged. Leaves stiff and erect. Leaves slender and mostly recurved. Leaves about ½" in diameter.       Leaves at least 1½" in diameter. Leaves with stomata; plants partially submerged, or emersed. Leaves green. Macrospores armed with spines. Macrospores without spines, merely crested or warted. Leaves 3'-3' long; macrospores less than 550 μ in diameter. Leaves 4'-8' long ; macrospores about 6ooμ in diameter. Leaves reddish, or rarely olive green. Leaves with stomata and bast bundles. Aquatic, but usually inhabiting the water's edge, sometimes completely emersed. Leaves from 12'-30' long; macrospores with convolute labyrinthine ridges. Leaves shorter; macrospores otherwise marked. Bast bundles only 4, except in some forms of I. Engelmanni. Monoecious. Macrospores coarsely crested. Macrospores merely reticulated. Polygamous; microspores rare. Bast bundles 4, with extra ones near periphery. Terrestrial, or rarely growing near water's edge.