SPHENOPTERIS. 105 
belonging to several families, are necessarily included in the 
definition which he has given." 
Since Brongniart’s time Sphenopteris has been subdivided by 
various writers into separate subgenera or genera. In such cases 
where the subdivision has been founded upon characters which are 
clearly of taxonomic value, the new terms proposed ought to be 
accepted as useful additions towards a rational classification of fossil 
ferns. On the other hand, to multiply terms for genera founded 
on characters admittedly of doubtful value, is hardly calculated to 
advance our knowledge of the botanical affinities of fossil forms. 
As an instance of such grouping we may refer to Schimper,’ who 
has instituted several types of Sphenopteris, based on resemblances 
of the purely vegetative organs to the fronds of existing genera. 
Until we know more of the fructification of fossil ferns, it is 
safer, and more consistent with our endeavours to avoid further 
unnecessary increase in the list of generic terms, already sadly too 
long, to make use of such genera as Sphenopteris under the older 
and more comprehensive sense. As evidence accumulates which 
is of real value, we shall sooner or later be in a position to make 
use of those standards of comparison which, in the case of 
recent ferns, are recognized as the most trustworthy bases for 
family and generic classification. 
For convenience sake the provisional genus Sphenopteris may be 
defined as follows :— 
Herbaceous plants, fronds bi- or tripinnate, venation of the types 
Sphenopteridis, Ctenopteridis, or Cyclopteridis; pinnules lobed, 
dentate or entire, tapering towards the point of attachment to 
the rachis, form varied, but frequently cuneate. 
Whilst making use of a definition such as this we must bear in 
mind that Sphenopteris, as a genus, is founded on general characters, 
and such as recur in distinct families and genera. Fontaine,* in 
the ‘Potomac Flora,” has called attention to the provisional 
nature of this genus; but, unfortunately, in his frequent use of 
recent generic names there does not always appear to be sufficient 
data to warrant a departure from the older, if less scientific, 
terminology. 
1 Hist. vég. foss. p. 169. 
? Trait. pal. vég. vol. i. 1869, p. 371. 
3 Potomac Flora, p. 89. 
