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

Family 11.   IsoetàceaeUnderw.Native Ferns 104.   1881.
Quillwort Family.

Aquatic or marsh plants rooting in the mud, with a short buried 2-lobed or 3-lobed trunk (stem) sending out abundant roots and sending up a compact tuft of rush-like leaves. Sporanges sessile in the axils of the leaves, some containing megaspores (megasporanges), others microspores (microsporanges); the former germinate into prothallia bearing only archegones, the latter into prothallia bearing usually only a single antherid.

The family consists of the following genus only.


1.   IsòetesL.Sp. Pl. 1100.   1753..

Submerged, amphibious or uliginous plants with a cluster of elongated awl-shaped leaves rising from a more or less 2-3-lobed fleshy short stem, the leaves with or without peripheral bast-bundles, with or without stomata, bearing a small membranous organ (ligule) above the base. Sporanges sessile in the excavated bases of the leaves, orbicular or ovoid, the sides more or less covered with a fold of the inner side of the leaf-base (velum). The sporanges of the outer leaves usually contain spherical, mostly sculptured macrospores, those of the inner ones contain minute powdery usually oblong microspores. [Name Greek, taken from Pliny, apparently referring to the persistent green leaves.]

About 60 species, widely distributed. Besides the following 2 are known from the southern United States, 7 from the Pacific Coast and 2 from Mexico. Owing to their aquatic habitat and apparently local distribution, these plants are popularly little known. The spores mature in summer and autumn. Type species: Isoetes lacustris L.

Leaves without peripheral bast bundles.
Leaves without stomata; plants submerged.
Leaves stiff and erect. 1. I. macrospora.
Leaves slender and mostly recurved.
Leaves about ½" in diameter. 2. I. Tuckermanii.
Leaves at least 1½" in diameter. 3. I. hieroglyphica.
Leaves with stomata; plants partially submerged, or emersed.
Leaves green.
Macrospores armed with spines. 4. I. Braunii.
Macrospores without spines, merely crested or warted.
Leaves 3'-3' long; macrospores less than 550 μ in diameter. 5. I. saccharata.
Leaves 4'-8' long ; macrospores about 6ooμ in diameter. 6. I. riparia.
Leaves reddish, or rarely olive green. 7. I. foveolata..
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. 8. I. Eatoni.
Leaves shorter; macrospores otherwise marked.
Bast bundles only 4, except in some forms of I. Engelmanni.
Macrospores coarsely crested. 9. I. Dodgei.
Macrospores merely reticulated. 10. I. Engelmanni.
Polygamous; microspores rare. 11. I. Gravesii.
Bast bundles 4, with extra ones near periphery. 12. I. melanopoda.
Terrestrial, or rarely growing near water's edge. 13. I. Butleri.


  1.  Isoetes macrósporaDurieu.
Lake Quillwort.   Fig. 118.

Isoetes macrospora Durieu, Bull. Soc. Bot. France, 11: 101. 1864.

Isoetes heterospora A. A. Eaton, Fernwort Papers 8. 1900.

Submerged or rarely above water in dry seasons; leaves 10-30, rigid, rather thick, scarcely tapering, dark or olive green, obtusely quadrangular, 2'-6' long; stomata none; peripheral bast-bundles wanting; sporange orbicular or broadly elliptic, unspotted; velum rather narrow; ligule triangular, short or somewhat elongated; macrospores 600-800 μ in diameter, marked all over with distinct or somewhat confluent crests, and bearing three converging ridges; microspores 30-46 μ long, smooth or papillose.

In 1°-5° of water, Labrador to the Northwest Territory, south to eastern Massachusetts and New Jersey. Formerly confused with Isoetes lacustris L., of the Old World.


2.  Isoetes TuckermániA. Br.
Tuckerman's Quillwort.   Fig. 119.

Isoetes Tuckermani A. Br. in A. Gray, Man. Ed. 5, 676. 1867.

Isoetes Tuckermani borealis A. A. Eaton, Fernwort Papers 10. 1900.

Isoetes Harveyi A. A. Eaton, Fernwort Papers 11. 1900.

Submerged or rarely partly or wholly emersed during very dry seasons; leaves 10-40, very slender, tapering, olive-green, quadrangular, 2–5 long, without peripheral bast-bundles, the outer recurved; sporange oblong, mostly white, its upper one-third covered by the velum; macroscpores 440-785 μ in diameter, with wavy somewhat parallel and branching ridges on the upper half, separated by the three converging ridges, the lower covered with an irregular network; microspores 26-42 μ long, nearly smooth, or with minute spines.

In ponds, Newfoundland to Massachusetts and Connecticut; clustered in shallow water.


  3.  Isoetes hieroglyphicaA. A. Eaton.
Warty Quillwort.   Fig. 120.

Isoetes hieroglyphica A. A. Eaton, Fernwort Papers 10. 1900.

Submerged with a bilobed trunk. Leaves 10-20, –3 long, blunt at the apex, without stomata; sporange spotted with dark cells, covered one-third to two-thirds by the velum; macrospores 486-720 μ in diameter, polished, covered with bold vermiform, subconfluent and somewhat reticulated ridges, becoming naked near the equator; microspores 31-44 μ in diameter, distinctly verrucose.

Nova Scotia to Quebec and Maine; usually growing in ponds and lakes.


4.  Isoetes BraùniiDurieu.
Braun's Quillwort.   Fig. 121.

Isoetes Braunii Durieu, Bull. Soc. Bot. France, 11: 101.  1864.

Isoetes echinospora var. Braunii Engelm. in A. Gray, Man. Ed. 5, 676.  1867.

Isoetes echinospora Boottii Engelm. in A. Gray, Man. Ed. 5, 676.  1867.

Isoetes echinospora robusta Engelm. Trans. St. Louis Acad. 4: 380.  1882.

Isoetes echinospora muricata Engelm. in A. Gray, Man. Ed. 5, 676.  1867.

Submerged or in dry seasons emersed, leaves 10-70, tapering, soft, green, 3'-12' long, without peripheral bastbundles, bearing stomata only toward the tip; sporange orbicular or broadly elliptic, spotted, one-half to threefourths covered with the velum; macrospores 400-620 μ in diameter, covered with broad spinules which are often slightly confluent and incised at the tips; microspores 25-32 μ long, smooth.

Labrador and Greenland to Alaska, south to New Jersey, Pennsylvania and California.


  5.  Isoetes saccharàtaEngelm.
Sugary Quillwort.   Fig. 122.

Isoetes saccharata Engelm. in A. Gray, Man. Ed. 5, 676. 1867.

Amphibious or uliginous with a flat depressed trunk. Leaves 10-30, green, pale at the base, spreading, 2'-5' long, quadrangular, bearing numerous stomata; sporange oblong, unspotted, with a narrow velum covering only one-fourth or one-third of its surface; peripheral bast-bundles wanting; ligule triangular, rather short; macrospores 420-510 μ in diameter, with very minute distinct or rarely confluent warts as if sprinkled with grains of sugar; microspores sparingly papillose, 22-30 μ long.

In mud overflowed by the tides, eastern Maryland and District of Columbia.


6.  Isoetes ripàriaEngelm.
Riverbank Ouillwort.   Fig. 123.

Isoetes riparia Engelm.; A. Br. Flora, 29: 178. 1846.

Amphibious or uliginous, usually emersed when mature; leaves 10-30, green, rather rigid, 4'-8' long, quadrangular, bearing numerous stomata; peripheral bast-bundles wanting; ligule rather short, triangular; sporange mostly oblong, distinctly spotted with groups of brown cells, one-fourth to three-fourths covered with the velum; macrospores 450-756 μ in diameter, marked with distinct or anastomosing jagged crests or somewhat reticulate on the lower side; microspores 28-32 μ long, more or less tuberculate.

Borders of the lower Delaware River.


  7.  Isoetes foveolàtaA. A. Eaton.
Pitted Quillwort.   Fig. 124.

Isoetes foveolata A. A. Eaton; Dodge, Ferns and Fern Allies of New Eng. 38. 1896.

Isoetes foveolata plenrospora A. A. Eaton, Rhodora 5: 280. 1903.

Amphibious from a bilobed or rarely trilobed base.   Leaves 15-70, stout, 2'-6' long, pinkish even when dry, or rarely dark green; stomata scattered, found only near the tips; no peripheral bast-bundles; monoicous or becoming dioicous; velum covering ¼ or ⅓ of the sporange; ligule round-ovate; sporanges thickly sprinkled with dark cells which are often collected in groups; macrospores 380-560 μ, covered beneath with very thick-walled reticulations, the openings appearing like little pits; reticulations elongate on the upper surface of the spore; microspores dark brown. 22-35 μ long, densely reticulate and usually slightly papillose.

In muddy banks, New Hampshire, Massachusetts and Connecticut.


8.  Isoetes ÈatoniDodge.
Eaton's Quillwort.   Fig. 125.

Isoetes Eatoni Dodge, Ferns and Fern Allies of New Eng. 39. 1896.

Amphibious from a large trunk ½'-1¼' in diameter.   Leaves of the submerged plant 30-200, varying in length up to 28', marked with an elevated ridge on the ventral side; leaves of the emersed plant shorter, 3-6; stomata abundant; peripheral bast-bundles irregular in occurrence or often wanting; velum covering ¼ of the sporange, polygamous; sporanges large, 0.4' by 0.15', pale spotted; macrospores small, 300-450 μ in diameter, marked with convolute labyrinthine ridges and cristate on the angles of the inner face; microspores 25-30 μ in diameter, minutely tuberculate.

In mud flats, New Hampshire to New Jersey.


  9.  Isoetes DódgeiA. A. Eaton.
Dodge's Quillwort.   Fig. 126.

Isoetes Dodgei A. A. Eaton, Fern Bull. 6: 6. 1898.

Isoetes canadensis A. A. Eaton, Proc. U. S. Nat. Mus. 23: 650. 1901.

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.


10.  Isoetes EngelmánniA. Br.
Engelmann's Quillwort.   Fig. 127.

Isoetes Engelmanni A. Br. Flora, 29: 178. 1846.

Isoetes Engelmanni fontana A. A. Eaton, Fern Bull. 13: 52. 1905.

Isoetes Engelmanni gracilis Engelm. in A. Gray, Man. Ed. 5, 677. 1867.

Isoetes Engelmanni valida Engelm. in A. Gray, Man. Ed. s, 677. 1867.


  11.  Isoetes GràvessiA.A. Eaton.
Grave's Quillwort.   Fig. 128.

Isoetes Gravesii A. A. Eaton, Fernwort Papers 14.  1900.


12.  Isoetes melanópodaJ. Gay.
Black-based Quillwort.   Fig. 129.

I. melanopoda J. Gay, Bull. Soc. Bot. France, 11: 102.  1864.


  13.  Isoetes bútleriEngelm.
Butler's Quillwort.   Fig. 130.

Isoetes Butleri Engelm. Coult. Bot. Gaz. 3: 1.  1878.