CLASSIFICATION. 



aggregated into small groups (sori) situated on the 

 veins at the back or margin of the frond ; more rarely the 

 sporangia are scattered over the whole of the lower surface. 

 Wall of the sporangia of one layer of cells and furnished with 

 an annulus (see glossary) which usually ruptures the wall by 

 its straightening. 1 



1. The Tree-fern Family. 



Stem erect, often tall with a terminal crown of very large 

 leaves. Sori rouud on a more or less convex hairy receptacle. 

 Sporangia sessile or stalked, obovoid, with a complete nearly 

 vertical annulu3. Indusium 1, Cyatheacea) (p. 129), 



2. The Common Fern Family. 



Stem usually rhizomatous. Leaves in a terminal crown 

 or scattered. Barren and fertile fronds sometimes dissimilar. 

 Sori or sporangia naked, or covered by the recurved leaf 

 margin, or by a variously shaped indusium. Sporangia with 

 a distinct pedicel, and with a vertical annulus, which is not 

 quite complete on one side. 2, Polypodiaceffl (p. 129). 



The Horned-fern Family. 



A marsh fern with heteromorphous leaves. Fertile fronds 

 with very narrow segments, their margins revolute. Spor- 

 angia sub-sessile, scattered dorsally on the nerves, not united 

 into sori. Annulus vertical nearly complete of very numerous 

 transversely elongated cells, or (in the same species) more or 

 less obsolete. Indusium ParkeriaceSB. 



To this family belongs the very interesting fern Ceratop- 

 teris thalictroides, Brogn., frequent in wet places. 



3. The Forked-fern Family. 



Ferns with a creeping rhizome and scattered dichoto~ 

 mously -branching stem-like fronds with, unlimited growth. 



1 Microscopical characters are omitted as far as possible : the 

 annulus can usually be seen with a good light and a pocket lens magni- 

 fying 10 diameters. 



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