5 



ISOETACEAE. 



VOL. 1. 



Family n. ISOETACEAE Underw. Native Ferns, 104. 1881. 



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 (megaspo ranges), others microspores (microsporanges) ; the former 

 germinate into prothallia bearing only archegones, the latter into prothallia bear- 

 ing usually only a single antherid. 



i. ISOETES L. Sp. PI. i too. 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.] 



The family consists of the following genus only. 



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. I. 7. macrospora. 



Leaves slender and mostly recurved. 



Leaves about l / 2 " in diameter. 2. I. Tnckermanii. 



Leaves at least 1^/2" in diameter. 3. 7. hieroglyphica. 



Leaves with stomata ; plants partially submerged, or emersed. 

 Leaves green. 



Macrospores armed with spines. 4. 7. Brannii. 



Macrospores without spines, merely crested or warted. 



Leaves z'-j,' long; macrospores less than 550/4 in diameter. 5. 7. saccharata. 



Leaves 4'-8' long ; macrospores about 6oo/x in diameter. 6. I. riparia. 



Leaves reddish, or rarely olive green. 7. 7. foveolata. 



Leaves with stomata and bast bundles. 



Aquatic, but usually inhabiting the water's edge, sometimes completely emersed. 

 Leaves from i2'~3o' long; macrospores with convolute labyrinthine ridges. 



8. 7. 



Leaves shorter ; macrospores otherwise marked. 



Bast bundles only 4, except in some forms of 7. Engelmanni. 

 Monoecious. 



Macrospores coarsely crested. 9. 7. 



Macrospores merely reticulated. 10. 7. 



Polygamous; microspores rare. u. /. 



Bast bundles 4, with extra ones near periphery. 12. 7. 



Terrestrial, or rarely growing near water's edge. 13. 7. 



Eatoni. 



Dodgei. 

 Engelmanni. 

 Gravesii 

 melanopoda. 

 Bit tier i. 



i. Isoetes macrospora Durieu. Lake Quill- 

 wort. Fig. 118. 



Isoetes macrospora Durieu, Bull. Soc. Bot. France, n : 



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 want- 

 ing; sporange orbicular or broadly elliptic, unspotted; 

 velum rather narrow ; ligule triangular, short or 

 somewhat elongated ; macrospores 600-800 M in 

 diameter, marked all over with distinct or somewhat 

 confluent crests, and bearing three converging ridges; 

 microspores 30-46 M long, smooth or papillose. 



In i-5 of water, Labrador to the Northwest Terri- 

 tory, south to eastern Massachusetts and New Jersey. 

 Formerly confused with Isoetes lacustris L., of the 

 Old World. 



