This section is from the book "An Illustrated Flora Of The Northern United States, Canada And The British Possessions Vol1", by Nathaniel Lord Britton, Addison Brown. Also available from Amazon: An Illustrated Flora of the Northern United States, Canada and the British Possessions. 3 Volume Set..
Plant amphibious from a bilobed trunk. Leaves 10-75, 8'-18' long when submersed, erect, or spirally ascending when scattered; emersed leaves 4'-6' long, tortuous and often interlaced, with numerous stomata and usually 4 bast-bundles; velum narrow, covering 1/5 to 1/4 of the sporange; sporanges thickly sprinkled with light brown cells; macrospores more numerous on submersed plants, globose, 500-675 μ in diameter, sparsely covered with irregular crests which at maturity separate into irregular groups leaving bare spaces, serrate or spinulose at the top; microspores more numerous on emersed plants, 22-44 μ, ashy, papillose or wrinkled.
Growing in mud flats, East Kingston, New Hampshire.
Isoetes Engelmanni A. Br. Flora. 29: 178. 1846. Isoetes Engelmanni fontana A. A. Eaton, Fern Bull. 13:
52. 1005. Isoetes Engelmanni gracilis Engelm. in A. Gray, Man.
Ed. 5, 677. 1867. Isoetes Engelmanni zalida Engelm. in A. Gray, Man.
Ed. 5, 677. 1867.
Amphibious, usually partly emersed when mature. Leaves 25-100, light green, quadrangular, tapering, o'-2o' long, bearing abundant stomata; peripheral bast-bundles present; monoecious; sporange oblong or linear-oblong, unspotted; velum narrow; macrospores 320-750 μ in diameter, covered with honeycomb-like reticulations; microspores 24-30 μ long, mostly smooth.
In ponds and ditches, rooting in mud. Maine to Virginia and Pennsylvania, Illinois and Missouri.
Isoetes Gravesii A. A. Eaton, Fernwort Papers 14. 1900.
Polygamous; leaves 20-150, 5'-11' long and 1" - 1 1/2" in diameter, erect, reddish or dark green; sporanges with an abundance of light brown cells, 1/5-1/3 covered by the velum; macrospores 351-405 μ in diameter, the upper hemisphere depressed, covered with short truncate single columns; microspores 22-30 μ long, high-cristate or tuberculate.
Edges of ponds and streams; Massachusetts and Connecticut.
1. melanopoda J. Gay, Bull. Soc. Bot. France, 11: 102. 1864. Terrestrial with a subglobose deeply 2-lobed trunk. Leaves 15-60, slender, erect, bright green, with a blackish shining base, 5'-18' long, triangular, bearing stromata throughout, well developed peripheral bast-bundles, thick dissepiments and small air cavities within; ligule triangular, awl-shaped; sporange mostly oblong, spotted, with a narrow velum; polygamous; macrospores 250-400 μ in diameter, with low more or less confluent tubercles, often united into worm-like wrinkles, or almost smooth; microspores 23-30 μ long, spinulose.