PTERTDOPHYl^A. 2g 



sporange ; polygamous; sporanges large, 10 by 4 mm., pale, spotted ; macrospores 

 small, 300-400 u in diameter, marked with convolute labyrinthine ridges and 

 cristate on the angles of the inner face ; microspores 25-30 u in diameter, smooth 

 or slightly papillose. In mud flats. E. Kingston and Epping, N. H. 



8. Isoetes Canadensis (Engelm.) A. Br. Plant amphibious from a 

 2-lobed trunk. Leaves 10-75, 2-4.5 dm. l°ng, when submersed, erect or spirally 

 ascending when scattered ; emersed leaves 10-15 cm. long, tortuous and often inter- 

 laced, with numerous stomata and usually lour bast- bundles ; velum narrow, cover- 

 ing from one-fifth to one -fourth of the sporange ; sporanges thickly sprinkled with 

 dark brown cells ; macrospores more numerous on submersed plants, globose 

 500-675 // 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, 22-40 /* in diameter, ashy, papillose. 

 In mud, Me. and Ont. to Mass. and Pa., and in Br. Col. (I. F. f. 106a.) 



9. Isoetes Engelmanni A. Br. (I. F. f. 107.) Amphibious, usually partly im- 

 mersed when mature. Leaves 25-100, light green, quadrangular, tapering, 22-50 

 cm. long, bearing abundant stomata ; peripheral bast-bundles present ; sporange 

 oblong or linear-oblong, unspotted ; velum narrow ; macrospores 400-520 jn in 

 diameter, covered with honeycomb-like reticulations ; microspores 24-28 ju long, 

 mostly smooth. In ponds and ditches, rooting in mud, Me. to Del. and Penn., 

 111. and Mo. 



Isoetes Engelmanni vdlida Engelm. Leaves 50-200, keeled on the upper side, 4.5-6 

 dm. long; sporange linear oblong, 1-2 cm. long, one-third to two-thirds covered by the 

 velum ; microspores 320-480 ^ in diameter ; microspores 24-27 /u, long, spinulose. War- 

 riorsmark, Cornwall and Smithville, Pa., and Wilmington, Del. 



Isoetes Engelmanni gracilis Engelm. Leaves 8-12, slender, 22-30 cm. long; bast- 

 bundles often quite small or only two present; spores as in the typical form. S. New 

 Eng. to X. J. 



10. Isoetes melanopoda J. Gay. (I. F. f. 108.) Terrestrial with a subglobose 

 deeply 2-lobed trunk. Leaves 15-60, slender, erect, bright green, with a blackish 

 shining base, 12-15 cm » l° n g< triangular, bearing stomata 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 ju in diameter with low more or less confluent 

 tubercles, often united into worm-like wrinkles, or almost smooth ; microspores 23- 

 28 /j. long spinulose. In moist prairies and overflowed fields, 111. to la., Mo. and 

 Tex. 



11. Isoetes Biitleri Engelm. (I. F. f. 109.) Terrestrial from a subglobose 

 trunk. Leaves 8-15, bright green, paler at the base, triangular, 4.5-18 cm. long, 

 bearing numerous stomata, and with well developed peripheral bast-bundles, thick 

 dissepiments and small air cavities within ; sporange usually oblong, spotted ; 

 velum very narrow or none ; ligule small, triangular ; dioecious ; macrospores 

 500-630 f.i in diameter, with distinct or confluent tubercles ; microspores 28-34 jlc 

 long, dark brown, papillose. On rocky hillsides, St. Louis, Mo., and on saline 

 flats, Ind. Terr. 



