ISOETACEJE. 147 



Va7\ Chapmani Engelm. Leaves about 30, floating, 18' 

 long; sporangia orbicular; niacrospores 0.44 — 0.55 mm. thick, 

 almost smooth on the upper side; microspores slightly papil- 

 lose, 0.027 — 0.030 mm. long. Near Mariana, Florida {Chap- 

 mati). 



§ 3. Terrestrial ; leaves nearly triangular, -with abundant 

 stomata and peripheral bast-bmidles, thick dissepiments and 

 small air-cavities. 



* Trunk bilobcd. 

 t Velum partial or almost watiting. 



13. I. melanopoda J. Gay. Polygamous; trunk sub-glo- 

 bose, deeply bilobed ; leaves 15 — 60, slender, stiff", erect, bright- 

 green, usually black at base, 5 — 10' or more long; sporangia 

 mostly oblong, 2" — 5" long, spotted, with a narrow velum; 

 ligula triangular awl-sliaped ; niacrospores 0.25 — 0.40 mm. 

 thick, with depressed tubercles often confluent into worm-like 

 wrinkles, or almost smooth ; microspores spinulose, 0.023 — 0.028 

 mm. long. \[ dr. pallida Engelm. is larger, with pale leaf-bases 

 and broader velum. Ringwood and Athens, Illinois {Hall); 

 Clinton, Iowa {Vasey) ; Limestone Gap, Indian Territory (But- 

 ler). The variety at Houston, Texas (Hall). 



14. I. maritima Unde. Monoecious; trunk small, only 

 slightly bilobed; leaves 8 — 15, rigid, green, i' — 2' long, y — f" 

 wide; sporangia oval, 2" long, \\" wide, brownish white, one 

 third to one half covered by the velum ; ligula small; macro- 

 spores 0.42 — 0.48 mm. thick, densely spinulose, the spines blunt, 

 rarely confluent; microspores smooth, white, 0.32 — 0.35 mm. 

 thick. In salt marsh, Alberni, Vancouver Island {Macoiin). 



15. I. Butleri Engelm. Dioecious; trunk sub-globose; 

 leaves 8 — 12, rigid, bright-green, 3' — 7' long; sporangia usually 

 oblong, spotted, with a very narrow velum or none ; ligula awd- 

 shaped from a triangular base; macrospores 0.50 — 0.63 mm. 

 thick, marked with knobs or warts, distinct or sometimes con- 

 fluent ; microspores papillose, dark-brown, 0.028 — 0.038 mm. 

 long. Var. immaculata Engelm. is larger, with unspotted 

 sporangia, and spinulose microspores, the macrospores 0.40 — 

 o 56 mm. In saline flats, near Limestone Gap, Indian Territory 



