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TRANS. ST. LOUIS ACAD. SCIENCE. 
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and I. echinospora var. Braun#, in Echo Lake the latter and /. lacustris, 
and in Europe not rarely this together with I. ec/tinospora. 
ft 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. 1. c.; Chapm. FI. 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 (about 30, 18 inches 
long) ; sporangium orbicular; spores larger, macrospores 0.44 to0.55 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 ij 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; yione of all of these 
had any mature microspores. Var. Chafmani 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 Nasturtium 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. 
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 18 inches long) ; sporangia 
