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 (megasporanges), 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. 1 100. 1753. 



Submerged, amphibious or uliginous plants with a cluster of elongated awl-sha'ped leaves 

 rising from a more or less 2-3-lobed fleshy short stem, the leaves with or without peripheral 

 bast-bundles, w-ith 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 laciistris L. 



Leaves without peripheral bast bundles. 



Leaves without stomata ; plants submerged. 



Leaves stiff and erect. i. /. macrospora. 



Leaves slender and mostly recurved. 



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



Leaves at least i l /2 H in diameter. 3. I. hieroglyphica. 



Leaves with stomata ; plants partially submerged, or emersed. 

 Leaves green. 



Macrospores armed with spines. 4. /. Brannii. 



Macrospores without spines, merely crested or warted. 



Leaves 2' -3' long; macrospores less than 550,14 in diameter. 

 Leaves 4 r -8' long; macrospores about 6oo/u in diameter. 

 Leaves reddish, or rarely olive green. 

 Leaves with stomata and bast bundles. 



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

 Leaves from IZ'-^Q' long; macrospores with convolute labyrinthine 



5- / 

 6. /. 



7- / 



emersed. 

 ridges. 

 8. L 



saccharata. 



riparia. 



foveolata. 



Leaves shorter ; macrospores otherwise marked. 



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

 Monoecious. 



Macrospores coarsely crested. 9. /. 



Macrospores merely reticulated. 10. /. 



Polygamous; microspores rare. n. /. 



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



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



Eatoni. 



Dodgei. 



Engclmanni. 



Gravesii 



melanopoda. 



Butleri. 



Lake Ouill- 



i. Isoetes macrospora Durieu. 

 wort. Fig. 1 1 8. 



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 v 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-s 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. 



