148 OUR NATIVE FERNS AND THEIR ALLIES. 



Var. Chapman! 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- 

 man). 



§ 3. Terrestrial ; leaves nearly triangular, with abundant 

 stomata and peripheral bast-bundles, thick dissepiments and 

 small air-cavities. 



* Trunk bilobed ; velum partial or almost wanting. 



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

 bose, deeply bilobed ; leaves 1 5 — 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). 



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

 slightly bilobed; leaves 8 — 15, rigid, green, i' — 2' long, J" — |" 

 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). 



18. 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 



