80 RUFFORDIA. 
Among recent ferns it is well known what striking variations 
occur in the vegetative structures within the limits of a single 
species. -Aspleniwm may be mentioned as one genus which shows 
this with sufficient clearness. 
In Pl. IV. is reproduced one of the most perfect specimens of 
RL. Gépperti. This is an excellent example of one end of the 
series, and represents the form of frond which is characterized by 
fine and narrow ultimate segments. 
In. Pl. V. Figs. 1-5 we have other specimens of what I regard 
as the same species. On comparing the figures of Pl. V. with 
those of Pl. 1V. and also Pl. VI. there are sufficiently obvious 
differences; these, however, consist mainly, if not entirely, in the 
relative size of the ultimate segments of the pinne, the general 
habit being practically identical in the two extreme forms. When 
a careful survey is taken of a large number of specimens, inter- 
mediate forms arrange themselves between the narrow and broad- 
leaved types; a few such forms are shown in Pl. V. In a case 
such as this, where we have no hiatus definite enough to admit of 
a specific difference, and where we have equally, if not more, 
striking instances of disparity in the size of leaf divisions among 
recent ferns, the most reasonable course to follow appears to be 
that of regarding the several forms as examples of one and the 
same species. It is but rarely that one district supplies such 
numerous and well-preserved samples of a local flora as that from 
which the British Museum material was obtained; and I cannot 
but think, that to create a number of ill-defined species, on such 
minor differences as are discoverable in this rich collection, would 
be to follow a course to which the paleobotanist is too often 
impelled by the scanty and imperfect data at his disposal. 
So far as the barren fronds or pinne are concerned there is a 
striking resemblance as regards habit to Asplenium fragrans, 
Sw. The variable size and shape of the ultimate segments, 
which form so marked a feature in the fossil, are still more 
striking in the recent fern. Under A. fragrans Hooker and 
Baker include a variety B. A. feniculaceum, H. and B., which 
has ‘‘narrowly linear”? ultimate segments, but the remark is 
added that ‘‘the two varieties seem to be quite connected by 
gradual and intermediate gradations.’’} 
1 Synopsis Filicum, p. 216, 
