466 THE GENUS ISOETES IN NORTH AMERICA. 
The plant is submerged in spring with the leaves partly floating; later, when the water recedes, the older leaves are 
spread out on the mud, but the later growth becomes erect; var. gracilis is often more or less submerged, and its 
weakly development is probably owing to this circumstance, while var. valida is the stoutest form we have, and one 
of the stoutest in the whole genus, perhaps only J. Malinveriana of the rice fields of Lombardy surpassing it. A very 
small form, only 5 inches high, has been collected in a springy place on a rocky hillside near Wilmington, Del., by 
A. Commons, otherwise not distinct. The Georgia variety, characterized by its larger spores, ought to be further 
studied. In my Missouri specimens I find, among many of the ordinary type with white sporangium, a few where 
this organ is uniformly brown, not spotted. The dissepiments of the leaves consist, the median of 3 to 4 and the 
transverse one of 2 to 3 layers of cells. The well-marked reticulation of the macrospores is formed of very thin, 
fragile lamin, not of thick ridges as in some other species, 
10. I. Howetin, Engelm, n. sp. Middle-sized, leaves (10 to 25) bright green (5 to 8 inches long) with thick 
dissepiments ; sporangium oval (14 to 2} lines long), unspotted, } to 4 covered by the velum ; subulate ligula as long 
as sporangium; macrospores 0.43 to 0.48 mm. in diam., rough, with prominent: rounded single or sometimes confluent 
tubercles, 
On border of ponds at the Dalles of the Columbia, Oregon, J. é T. J. Howell, 1880, not quite mature in June. 
I insert this species, which has just been communicated to me through the kindness of Mr. G. E, Davenport, while 
the manuscript is in the hands of the printer ; this must excuse some discrepancies in the foregoing pages, where no 
reference could be made to it. The new species is distinguished from the similar J. Bolanderi by the longer leaves, 
larger, more prominently marked macrospores, and especially by the distinct peripheral bast-bundles, which place it 
near the foregoing one, by the thick dissepiment consisting of 4 to 6 layers of cells, and by the unusually narrow 
and long ligula ; the tubercles of the spores are quite prominent, as high as they are wide, rounded at top; micro- 
spores light brown, smooth. — Among the specimens of this species, and probably collected with it, I find a single one 
similar in the structure of the leaf, but without a trace of a velum, the sporangium being entirely naked, and only 
attached by the median line to the leaf base; it is unfortunately immature, and can only be pire as a probably 
new species, J. nuda. This would not be the first instance of two species growing together in the 
pond or lake; in Mystic Pond we find I. Tuckermani and I. echinospora, var. oe in Echo aks ‘e [386 (29)] 
latter and J. lacustris, and in Europe not rarely this together with I. echinospora 
tt Velum complete. 
I. FLaccrpA, Shuttleworth, in sched. A slender plant of light green color ; leaves often very long, 10 to 35 
in eae, 15 to 24 inches long, sometimes entirely submerged, or partly floating on the surface, or cna 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, datznat or confluent into labyrinthiform wshildes micro- 
spores 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); sporanginm orbicular ; spores 
larger, res 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 Talla- 
hassee ; 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 1} 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 ; not one of all these had any mature microspores. Var. 
mt was discovered by A. W. Chapman near Marianas, 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 lacustre; but the Isoétes has not been seen in 
it since: its larger macrospores, sometimes 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, snc seael evidently often in deep water, the leaves elongate, seek the surface and float on it. The closed 
velum and the peculiar sculpture of the macrospores readily distinguish it from its allies. 
C. Terrestrial species, maturing when entirely out of water, with rere stomata and peripheral bast-bundles, thick 
dissepiments, and small air cavities in the nearly triangular lea 
* Velum partial or almost wan 
12. I. meLanopopa, J. Gay. Polygamous; trunk subglobose, pit 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 mostly 
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