DESCRIPTIONS OF SPECIES. 9 



upper and under surface of the frond, the variation of form of the pinnae of 

 different fronds, and different parts of the same frond. 



The robust habit of this plant, the strong, waved, and reticulated ner- 

 vation and broadly winged rachis, which seem to distinguish it at a glance 

 from all known fossil species, suggested a comparison with some of the 

 strong-growing tropical ferns, and it was only after a laborious examination 

 of all the genera of exotic ferns contained in the herbaria to which I had 

 access that I was led to turn m} r eyes nearer home, and found in Onoclea 

 a striking' and unexpected resemblance to it. 



The common form of Onoclea- sensibilis grows abundantly in all parts 

 of our country, and is one of the first plants collected by the youthful 

 botanist. In this we have the rachis of the frond more or less winged, and 

 a nervation on the same general plan with that of the fern in question, but 

 more distinctly reticulated than in some specimens of the fossil. (See PI. 



XXIII, fig. 4.) By this I was at first misled, but in examining Dr. Torrey's 

 var. obtusilobatus I found the exact counterpart of the exceptional forms 

 in the lobation of the pinnae and in the nervation. (See PL XXIII, figs. 

 5, 6.) The gradation of characters in this variety is very great. In some 

 specimens we have a distinctly bipinnate frond; the pinnae composed of 

 numerous remote, even obovate, pinnules, and the nervation not reticulated, 

 the nerves of the pinnules radiating and forked, but never joining. This 

 is the extreme form, but even here the rachis of the frond is more or less 

 winged. In an intermediate form we find the rachis winged, the pinnae 

 deeply lobed, and precisely the nervation of the fossil. Even in the 

 common form the nervation is similar in plan, and the elongated spaces, 

 destitute of nerve branches on either side of the rachis of the pinnae, form 

 a noticeable feature in both. 



The general aspect of the frond and the nervation in some species of 

 Woodwardia is not unlike that of the fossil now figured, and until we shall 

 have found the fruit it will not be possible to prove that this is Onoclea and 

 not Woodwardia. The resemblance of the fossil to Onoclea in the form of 

 the frond, the lobation of the pinnules, and in the style of nervation is, 

 however, stronger than to Woodwardia, as will be seen by a comparison of 

 PI. XXIII, fig. 4 — a portion of the frond of the living Onoclea — with PI. 



XXIV, figs. 4 and 5, corresponding portions of the fossil. Among the large 

 number of specimens obtained of this fossil fern there are none which 



