Fig. 352.
- a. Sphenopteris crenata.
- b. The same, magnified.
(Foss. Flo. 101.)
Fig. 353.
Caulopteris primæva, Lindley.
All the recent tree-ferns belong to one tribe (Polypodiaceæ), and to a small number only of genera in that tribe, in which the surface of the trunk is marked with scars, or cicatrices, left after the fall of the fronds. These scars resemble those of Caulopteris (see [fig. 353.]). No less than 250 ferns have already been obtained from the coal strata; and even if we make some reduction on the ground of varieties which have been mistaken, in the absence of their fructification, for species, still the result is singular, because the whole of Europe affords at present no more than 50 indigenous species.