10 HORSETAILS.—FERNS. 
a continued advancement in complexity of structure, vessels of 
different kinds make their appearance for the first time, and 
the stems are frequently of considerable size and height. Cala- 
“ay Ny 
Wve? od 
ee 
ih <= 
aA 
A’ 
Fig. 14. The Male Fern (Aspidinm Filix-mas).—Fig. 15. A Tree-fern, show- 
ing a tuft of leaves (fronds) at the apex of a cylindrical stem, which is 
enlarged at its base, 7a, by the development of a mass of aerial adven- 
titious roots. 
mites, an order of plants nearly allied to the Horsetails, and 
which were extremely abundant during the formation of our coal 
measures, would appear to have reached the height of our loftiest 
