ISOETACEJ5. 147 



Var. Chapmani Engelm. Leaves about 30, floating, 18' 

 long; sporangia orbicular; macrospores 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- 

 maii) . 



3. Terrestrial ; leaves nearly triangular, with abundant 

 stomata and peripheral bast-bundles, thick dissepiments and 

 small air-cavities. 



* Trunk bilobed. 

 t Velum partial or almost wanting. 



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-shaped ; macrospores 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. Var. 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, " f" 

 wide; sporangia oval, 2" long, ij" 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 (Macoun). 



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 awl- 

 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 

 0.56 mm, In saline flats, near Limestone Gap, Indian Territory 



