CRYPTOGAMIA, FILICES. 253° : 
- 
Sixczss. 1.€. vestita, Mephrodium lanosum. Mich, FI. 
Am. 2. p. 270. 2. _Px. Ons. Fronds 2 or 3 inches 
high, glaucous “white and pulverulent on the — 
under side; stipes brown. Has. In the crevices of rocks on 
the banks of the Missouri about 50 miles above its con- 
fluence; rare. v. v. ce y 
330. DICKSONIA. L’Heritier. — 
Sori punctiform, marginal, roundish, and dis- 
5 
coe 
tinct. Indusium double, one superficial, opening 
{ outwards, the other marginal and opening in- 
{ - Ww ards. 
f . Species. 1. D. pilosiuscuia. Common in Penneginams 
& ‘and New Jersey. 
~ A small genus of tropical ferns, consisting of deat 2 ae 
23 species of which there is an arborescent species in the | 
- island of St. Helena, and another in the Seuth-sea islands. * 
. HYMENOPHYLLUM. Smith. 
Sorus marginal, inserted in a cylindric recep- 
tacle. Indusium two-valved, including the sorus. 
Species. 1.H. ciliatum—A genus of more than 20 
species, producing small diaphanous and membranaceous 
fronds. 
$32. ISOETES: 1. (Quill-wort.) a 2 
ae 
; ieee 
Capsule membranaccous, not opening, 1-cel- 
led, immersed in the base of the frond. Seeds 
angular, attached to many filiform receptacles. 
Species. 1. ddcustris, Abundant along the inundated, 
gravelly and mirey shores of the Delaware, near Philadei-— 
phia and other emg also in the state of New York. 
Ops. Root fibroas, fibres simple, broad and fistulous; 
fronds dilated and imbricate at the base, narrow and sub-— 
ulate, above flat, beneath angularly convex, each pro-_ 
ducing 4 fistulous caviues. Fruit monoicous; sori cordate- 
oval, immersed in a corresponding cavity at the base of 
the frond, partly bilobed, included in a membranaceous 
integument connected together by numerous transverse 
columnar receptacles; male! sorus filled with pulverulent — 
pollen, becoming white on drying; capsules (or seeds) glo- — 
bular, when dry presenting a snow-white Pereralees, ‘ 
