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HYDROPTERIDES. 
Suborder II. SALVINIEiE. (The Salvinia Family.) 
Floating branching plants, with alternate and imbricated cellular 
leaves; the sporocarps borne on the stem or branches underneath. 
(Aspect of Liverworts.) 
2. Salvinia. Sporocarps clustered on short leafless branches turn¬ 
ed downward and immersed, surrounded by long rootlets. 
3. Azolla. Sporocarps sessile at the forks of the frond or along 
the under side, bursting transversely or irregularly. 
1. ISOETES, L. Quillwort. 
Stem a mere succulent disk, rooting from underneath, and cov¬ 
ered above with the dilated imbricated bases of the elongated terete 
awl-shapedo r stalk-like cellular leaves. Sporocarps ovoid and 
plano-convex, pretty large, sessile in the axils of the leaves and 
adherent to their excavated dilated base, covered by an interior scale, 
very thin, indehiscent, traversed internally by transverse threads 
forming a kind of partitions; those of the central leaves filled with 
very minute powdery grains (analogous to the spores of Lycopodi¬ 
um) , the exterior filled with larger spherical-quadrangular spores 
{oophoridia) , at first cohering in fours, their crustaceous integu¬ 
ment traversed by 3 radiant lines. (Name composed of urosj 
equal, and eros, year , i. e. alike the year through.) 
1- I* lacustris, L. Disk-like rootstock broad and depressed ; 
leaves wholly submersed, dark green, rigid and fragile, awl-shaped 
(2 -6' long), the dilated base as broad as long; spores (oophoridia) 
roughish-granulated, scarcely reticulated. — Bottom of ponds and slow 
streams, not rare northward. — New England specimens agree well 
with the N. European plant, and also seem too nearly like the next. 
E 1’iparia, Engelm. Rootstock small; leaves slender, soft, 
yellowish-green (^-G* long), the base broader than long; spores 
minutely farinaceous and reticulated. — Gravelly banks of the Dela¬ 
ware below Philadelphia, between high and low water mark, Dr. 
Zantzinger: probably throughout the Middle States. 
E Ellgelliniiini, Braun. Leaves long and slender (9 / —12 / 
long), entirely emersed in summer, soft and flaccid, light yellowish- 
green, the dilated base longer than broad ; spores coarsely farina¬ 
ceous and reticulated. — Shallow ponds of the Western States. 
2* SALVINIA, Micheli. Salvinia. 
Stem filiform, floating free, bearing sessile entire leaves above ; 
and the fructification on short leafless branches from the under 
