INTRODUCTION. 
densely clustered at the top into a large upright raceme, which gradually in- 
creases in size, in consequence of the leaflets of the frond becoming changed 
into similar clusters of theca;, and thus proving the origin of the whole. 
GEOGRAPHY. — As the order contains but one British plant, the above is 
a description of a single individual ; it is the largest of our Ferns, inhabiting 
woody and swampy situations, adding beauty to a foreground, but scarcely of 
farther utility. Gerard tells us that it was used in his time for inward bruises. 
OPHIOGLOSSACEiE. 
( Contains Botrychium and Ophioglossum.) 
Ophioglossacea, Br., Lind., %c. ; — Ophioglosse a, Spreng. ; — Filices, 
Linn., Smith, Hook., §c.; — Stachiopterides, Wit Id. ; — Bivalvia , Hqff'm. ; 
Yalvata, Web., Mohr.; — Agyrata, Swz. 
The two plants contained in this order are very near in general structure- 
to the last order, yet in some important particulars they differ very ma- 
terially. Their root is smooth, fibrous and yellow, not creeping, nor hairy : 
and giving rise to one or at most two fronds only, which issue from the 
ground with a straight and not circinate vernation. The frond half way up 
divides into a leafy expansion exactly similar in its dichotomously branched 
veins, reticulated cuticle, cellular substance, and numerous stomata, to that of 
the Polypodiacee. The theca are sessile, opaque, ringless, smooth, collected 
into a simple or compound spike, and are supposed to arise as in the last 
described order, from the leaf itself. The thee® open by a regular 
transverse fissure, emitting smooth, yellow, very minute seeds, those of 
Botrychium in pairs. The stems of both genera are perennial, herbaceous, and 
hollow, that of Botrychium containing its ducts in two bundles near the centre 
of the stem, that of Ophioglossum in from five to seven bundles, seated 
between two cylindrical cuticles, and by their pressure forcing the inner one 
into a tortuous form. 
ISOETACEiE. 
( Containing Isoetes only.) 
Lycopodiacea, Lind., Decan., Brongn. ; — Marsileace.e, Hook. ; — Miscel- 
lanea, Part of Rhizosperma, Rhizopterides, Hydropterides, &c. 
The genus Isoetes has in all arrangements of British plants been associated 
with Pilularia, on account of their both being water plants, both having round 
and filiform leaves, and two kinds of grains or capsules ; but, except in these 
B 
