1 6 WHERE TO FIND FERNS. 



each two cotyledons a cotyledon being a seed-lobe, and, 

 for assimilative purposes, a seed-leaf whether developed 

 above ground or beneath the soil ; 2, seeds which 

 have each one cotyledon; and, 3, seeds, without coty- 

 ledons, such as are the spores of cryptogamic plants. 



Under the same system there are in the class of 

 Acotyledons nine orders, of which ferns -filices con- 

 stitute the first. The orders are subdivided into 

 tribes, the tribes into genera, and these into species and 

 varieties. Under filices there are four tribes, nineteen 

 genera, forty-five species, and almost endless varieties. 

 Here we shall only take note of genera and species, 

 and the descriptive and enumerative parts of the volume 

 will thus be found divided into forty-five sections, 

 headed by the common and botanical name of each 

 species of British fern. But, before leaving the present 

 chapter, we shall say a little about fern-spores, and 

 indicate the classification adopted by botanists with 

 regard to British ferns in so far as it is based upon 

 the character of the spore-cases, and the character of 

 the unrolling fronds. 



British ferns, then, are divided for purposes of 

 classification into three groups, named, i, POLY- 

 PODIACEJE ; 2, OSMUNDACEJE ; and, 3, OPHIOGLOSSACE^. 

 The first group, Polypodiacea, includes ten smaller 

 groups, comprising fifteen genera : viz. : Polypodium, 

 Allosurus, Gynmogramma, Polystichum, Lastrea, Athy- 

 rium, Aspleniiitti, Scolopendrium, Blechnum, Pteris, 

 Adiantum, Cystopteris, Woodsia, Trichomanes, and Hy- 

 menophyllum. The spore-cases in this group are girt by 

 an elastic ring which, on bursting, causes the spore-case 

 to open by what is called a "transverse fracture." 

 The form of the case, the elastic ring, the manner 

 in which it opens, and the shape of the spores 

 enclosed in it are illustrated by the diagrams which 

 follow, and which exhibit the Common Polypody 

 (Polypodium vulgare\ with a portion of its rhizoma, 



