386 TRANS. ST. LOUIS ACAD. SCIENCE. 



and /. echinospora van Braunii, in Echo Lake the latter and /. lacustris, 

 and in Europe not rarely this together with /. echino^pora. 

 \ t Velum complete. 



11. I. FLACCIDA, Shuttleworth, in sched. A slender plant of light green 

 color; leaves often very long, 10 to 35 in number, 15 to 24 inches long, 

 sometimes entirely submerged, or partly floating on the surface, or entirely 

 emerged; sporangia oval, 2 to 3 lines long, entirely covered by the velum ; 

 macrospores 0.30 to 0.42 mm. in diam., covered with many or rarely few 

 comparatively large flattish tubercles, distinct or confluent into labyrinthi- 

 form wrinkles; microspores not seen. — A. Braun in Flora 1. c. ; Amer. 

 Jour. I.e.; Chapm. Fl. So. States, p. 602. 



Var. RiGiDA, a smaller form with still more slender, erect, dark green 

 leaves (about 10 to 15 in number, 5 to 6 inches long). 



Var. Chapmani larger, light green, leaves floating (abovit 30, iS inches 

 long) ; sporangium orbicular; spores larger, macrospores 0.44 to 0.55 mm. 

 in diam., marked as the type, or, especially on the upper side, almost 

 smooth; microspores 0.027 to 0.030 mm. long, slightly papillose. 



Florida, on the muddy bottom of lakes or swamps, first found by Dr. 

 Rugel in Lake Immonia, north of Tallahassee; lately rediscovered by A. 

 P. Garber in a hummock, near Manatee, on the muddy border of shallow 

 ponds in water from a few inches to i J feet deep, the long leaves floating 

 or spread out on the mud, the inner ones erect; mature in April and May. 

 disappearing in June. Var. rigida was found by the same collector on 

 the wet borders of Lake Flirt, not far from Lake Okeechobee, in August, 

 entirely emersed and erect. Mr. A. H. Curtiss seems to have met with 

 a similar form in a muddy swamp on Indian river; none of all of these 

 had any mature microspores. Var. Chapmani was discovered by A. W. 

 Chapman near Mariana, West Florida, filling a lakelet of pure limestone 

 water about one foot deep, formed by one of those (in that region so 

 common) subterranean streams, where it comes to the surface before 

 emptying into Chipola river, together with Na^turtitim lacustres ; but 

 the Isoetes has not been seen in it since : its larger macrospores, some- 

 times quite smooth, distinguish it from the other forms. — This peculiar 

 species, the only one thus far found in Florida, is distributed over the 

 whole State. It cannot be classed with the submerged species, for, though 

 evidently often in deep water, the leaves elongate, seek the surface and 

 float on it. The closed velum and the peculiar sculpture of the macro- 

 spores readily distinguish it from its allies. 



C. Terrestrial species, maturing when entirely out of water, with abundant sto- 

 mata and peripheral bast-bundles, thick dissepiments, and small air cavities 

 in the nearly triangular leaves. 



* Velum partial or almost wanting. 



12. I. MELANOPODA. J. Gay. Polygamous ; trunk subglobose deeply 

 bilobed; leaves slender, stiff", erect, bright green, usually black at base 

 (15 to 60 in number, 5 to 10 or rarely even iS inches long) ; sporangia 



