INTRODUCTION. 7 
exposed, yet few plants suffer more from a contaminated atmosphere than this 
tribe. Cryptogramma Crispa, Grammitis Ceterach, Aspidium Lonchltis, 
Asplenium lanceolatum, marinum, viride and septentrionale, seem to languish 
for their native freedom. They require the shelter of a frame or greenhouse to 
compensate for the purity of the air of their lofty or exposed homes. 
Ferns are easily propagated from the spores, nothing more being necessary 
than putting into a garden pot some stones or broken rubbish to within two 
inches of the top, covering these with an inch in depth of very finely sifted 
sandy loam, and then sowing the spores upon it, covering the whole with a flat 
piece of glass, and placing it in a green house. 
VIRTUES. — The uses of the Ferns are not very conspicuous. Their bitter 
principle renders them unpalatable to all creatures. Neither men nor brutes 
employ any species as an article of food, unless driven by the necessity of 
hunger ; and even the little insects that infest herbaria refuse to prey upon 
them. They are not, however, wholly useless either in medicine or the arts. 
Their nauseous taste renders them efficacious in expelling intestinal worms ; 
some of them have been used as a substitute for hops in brewing, and with 
better success than most other plants, on account of the tannin and gallic acid 
they contain, precipitating the feculent matter in the wort. The same con- 
stituent principle renders them also serviceable in preparing kid and other 
light leathers, and they yield much comparatively pure potass when burnt. 
The dried fronds of the common brakes are valuable to pack fruit in, and as they 
retain moisture less, are much better than straw to shield garden plants from 
frost. Except for these uses, the British Ferns have been little employed, 
unless, indeed, for those purposes to which most plants when dry are available, 
namely, for thatch, for fodder, and for fuel. 
HYMENOPHYLLACEiE. 
( Containing the Genera Hymenophyllum aud Trichomanes. ) 
Triciiomanoideai, Kaulf. ; Filices desciscentes, Spreng. ; — Part of 
Gyrate, Annulate, Polypodiace^e, Gleicheniace.e, Filices ver^e, 
Hymenophylleae, &c. of Authors. 
STRUCTURE. — The two plants contained in this order long maintained a 
situation among the dorsal Ferns, though improperly, because their fruit is not 
dorsal but marginal, growing in a distinct and differently organised receptacle. 
The annulus corresponds in its functions, jointed appearance, and elasticity, to 
those of the last tribe, except that instead of its being a continuation of the 
foot stalk of the theca, it is placed obliquely or transversely, and of conse- 
quence the theca bursts vertically. For this reason, Hymenophyllum and 
