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254 F E R N S O F NORTH AM E R IC A .
as that which serves for our figure, and again pinnate with
rhomboid-ovate incised and toothed pinnæ in still larger
plants. The teeth are generally obtuse, and if pointed are
still muticous or destitute of the mucronate or spinulose point
which is always seen in A . aculeahnn and our other common
species of this section.
The sori are abundant on the upper pinnæ, and are placed
mostly near the midveins of the lobes. The indusia are very
large, orbicular, nearly entire, and often slightly wrinkled on
the surface. They often lap over each other a little, so as to
be slightly imbricated. The spores are ovoid and have an
uneven surface.
The form of Aspidiiini aculeatum to which the name of
var. scopzdhmni was given at page 125 of this volume is
almost as much like A . mohrioides as it is like A . aculeatum,
but as it has the lobes of the pinnæ somewhat aculeate it is
better to leave it with the latter species.
The specific name mohrioides refers to the considerable
resemblance the fronds of this species have to those of Mohria
thurifraga, a schizæaceous fern of South Africa.
Plate LX X X .— Fig. 4-9. Aspidium mohrioides, from California, a
small specimen. Fig. 5 is an enlarged pinna. Fig. 6 is a pinnule, one
of the indusia removed and more magnified at Fig. 7. Fig. 8 is a
spore, and Fig. 9, a scale from the rachis, both more or less magnified.
P l a t e L X X X .— F ig . 1 0 - 1 4 .
C E R A T O P T E R IS TH A L IC T RO ID E S , B r o n g n i a r t .
Floating Fern.
C e r a t o p t e r i s t h a l i c t r o i d e s ;—^Plant aquatic, annual;
stalks thick, succulent, full of air vesicles; fronds fiaccid,
half-succulent, often proliferous from the surface or the edges ;
the earliest sterile ones floating, ovate, simple or three-lobed;
later ones larger and more compound, the largest of them a
foot long, erect, ovate in outline, twice or thrice pinnate with
ample triangular-ovate divisions which are adnate to a winged
midrib; veins finely reticulated into oblong-hexagonal meshes,
the areoles pellucid-dotted; fertile fronds taller than the sterile,
decompound with very numerous narrowly linear confluent
segments; margins recurved and concealing the sub-globose
sessile sporangia scattered on longitudinal veins or receptacles;
ring of sporangia very broad, sometimes nearly complete,
often much reduced or even wanting.
Ceratopteris thalictroides, B ro n g n ia r t , “ in Bulletin Soc. Philom., 18 2 1,
p. 184, t. i. ’’— H o o k e r , Gen. F i l , t. x ii; Sp. Fil., ü., p. 235.—
B r a c k e n r id g e , Ferns of U. S. Fxpl. Exped., p. 67.— M e t t e n
iu s , F II. Hort. Lips., p. 39.— M o o r e , Index., p. 2 3 0 .— G r i s e b
a ch , PI, B r it . W. I. Islands, p. 672.— H o o k e r & B a k e r , Syn.
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