147 
PARKERIA PTERIDOIDES. 
Pten's-like Parkeria, 
CRYPTOGAMIA FILICES— Nat. Ord. PARKERIACEJE. 
Capsulm sphsericse, uniloculares, membranacese, emnnulatce, indehiscentes, intus semini- 
bus majusculis repletae. Sori dorsales, venis longitudinalibus, costae parallelis in- 
serti, marginales, continui. Indusium e margine frondis continuum, intus liberuni. 
— Plantse aquatica. Radices e basi frondium longm, ramoscB, tomentosce. Frondes di- 
chotome divisi, ramis frmtificantibus linearibus, venis longitudinalibus, paululum anasto- 
mosantibus. Vernatio circinnata. Habitus Pteridis sed capsules valde dissimiles. 
Gen. Char. — Idem ac Char. Ord. 
Parkeria pteridoides ; frondibus uniformibus. 
Aquatic. The roots long, penetrating deep into the mud, branched, and 
downy with numerous small, black, scale-like processes. Plant from 
8 inches to a foot in height. Stipes 4 or 5 inches long, stout, cy- 
lindrical (?), obscurely striated, furnished with a few small brownish 
scales, and often throwing up from the base a young circinnate frond. 
Frond subtriangular in its circumscription, bipinnatifid, the segments 
linear, once or twice dichotomous, the ultimate ramuli rather acute. 
The anterior side of the frond is slightly convex, marked with about 
3 longitudjinal continuous nerves, which here and there anastomose ; 
the posterior side is nearly plane. 
Involucre, or Indusitim, formed by the involute margin of the frond, which 
is thin, membranaceous, and reticulated. In the older and broader parts 
of the frond there is a rather considerable space in the centre, between 
the margins of the involucre (Fig. 2.) ; but in the ultimate branches, 
where the frond is narrower, the margins of the involucre almost meet 
in the centre, (Fig. 4.) These involucres cover and conceal the sori or 
clusters of fructification, which are inserted continuously upon the veins. 
Capsule large in proportion to the size of the plant, spherical, thin, 
membranaceous, with numerous swellings caused by the seeds within, 
almost transparent, sessile, of a brownish colour. Within, they contain 
numerous, rather large, spherical, or frequently angular, pale brown 
seeds. 
The general appearance of this curious fern, impressed me 
with the opinion that it belonged to the genus Pteris ; a more 
accurate examination subsequently demonstrated, not only that 
its structure was incompatible with the characters of that ge- 
nus, but also that it was equally at variance with the definition 
of the Natural Order Filices. It is essential to the true Ferns, 
to possess a capsule which opens either with a regular fissure, 
or by means of an elastic annulus, and no appearance of that 
kind is discoverable in the individual before us. 
As a new genus, then, I have the utmost pleasure in dedi- 
cating this plant to its discoverer C. S. Parker, Esq. of Blo- 
VOL. II. 
