80 RT7FFORDIA. 



Among recent ferns it is well known what striking variations 

 occur in the vegetative structures within the limits of a single 

 species. Asplenium may be mentioned as one genus which shows 

 this with sufficient clearness. 



In PI. IV. is reproduced one of the most perfect specimens of 

 R. Gopperti. 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 PI. Y. Figs. 1-5 we have other specimens of what I regard 

 as the same species. On comparing the figures of PI. Y. with 

 those of PI. 1Y. and also PI. VI. there are sufficiently obvious 

 differences ; these, however, consist mainly, if not entirely, in the 

 relative size of the ultimate segments of the pinnae, 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 Y. 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 palaeobotanist is too often 

 impelled by the scanty and imperfect data at his disposal. 



So far as the barren fronds or pinnae are concerned there is a 

 striking resemblance as regards habit to Asplenium fragrant, 

 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. frograns Hooker and 

 Baker include a variety p. A. faniculaceum, 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 



1 Synopsis Filicum, p. 216. 



