54 On the North American Species of Isoétes and Marsilea. 
hilly country southwest of St. Louis,* in the warm climate of 
Missouri, with Cephalanthus, Lycopus angustifolius, several 
uscute, Sagittarie, Polygona, Leersie, etc. In winter and 
spring it is covered by water, but late in summer and in the fall 
the ground on which it grows is mostly dry, or nearly so. It 
forms thick tufts with many leaves, 9 to 12 inches long, of a 
bright yellowish green color. The rhizoma is also flat, depressed, 
and often one inch in diameter. The sheath or dilated base of 
the leaf, which bears the sporangia, is longer, and the sporangia 
themselves somewhat larger, than in any of the other species. — 
I. riparia has been described from specimens collected by Dr. 
Wm. Zantzinger on the banks of the Delaware below Philadel- 
phia. It grows there with Sagitlaria pusilla, Eriocaulon fla- 
tion specimens of the Isoétes found in Pennsylvania, on ‘“ ponds 
and shaded wet places,” mentioned by Darlington in his Flora 
Cestrica, nor any from New York, etc., and it is not known 
whether they are identical with J. riparia or not. 
I. setacea is common in the south of Europe (especially the 
south of France and Sardinia) and also in northern Africa, and is 
sufficiently well known. The tufts are always smaller than those 
[ 4. lacustris and I. Engelmanni, but larger than in J. riparia ; 
he leaves are still more narrow and slender than in the last spe- 
cies, and 8 to 12 inches long. 
" ida was discovered by Mr. Rugel in Lake Tamonia, 
Florida, and first distinguished and named by R. J. Shuttleworth, 
Esq. It has a small roundish rhizoma, and leaves 18 to 24 inches 
long, as slender as in J. setacea, but of thinner texture, and some- 
what transparent. ‘The sporangia are smaller, and the spores by 
far the smallest of all the species. Iam not now prepared to de- 
cide, what relation this species bears to J. longissima, Bory, from 
Lake Houbeira, in Algeria, or to an Isoétes from California, which 
Prof. Kunze considers as identical with J. longissima, but which 
more probably stands near the Florida species, or is identical with. it. 
Pn a le 
* The places where it has been collected by me as late as 1842, are now chan 
by cultivation, or the vegetation destroyed by hogs and ducks. | have not been ° 
nd it since, but doubt not that it still inhabits more secluded ponds in this 
remarkable region, where the strata of the carboniferous or mountain limestone 
offer in their numberless “ sink-holes” (originating undoubtedly from the caving in 
of the roof of caverns, and peculiar, in this neighborhood at feast, to this forma- 
tion) many localities of a similar description.—G. E. 
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