EOCENE FERNS. 



75 



during the cooler Miocene, thus giving it a European origin. Its existing distribution in 

 Asia and America entirely favours the theory that it spread from the Greenlandic centre, 

 and its occurrence at Mull only traces its origin still farther back to Eocene Europe. 



The following very valuable remarks by Prof. Newberry^ supplement our knowledge of 

 this Fern : — " The collection of Dr. Hayden contains a great number of examples of this 

 beautiful Fern, showing the upper and under surface of the frond, the variation of form of 

 the pinnas of different fronds^ and different parts of the same frond. The robust habit 

 of this plant, the strong, waved and reticulated nervation, and broadly waved 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, or described by authors, that I was led to turn my eyes nearer home. The 

 common form 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 

 fossil before us, but more distinctly reticulated. By this I was at first misled, but in 

 examining Dr. Torrey's var. obtusilohata, I found in some specimens the exact counter- 

 part of our fossil in the lobation of the pinnae and nervation. The gradation of characters 

 in this variety is very great and interesting. 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." The agreement in character with our fig. 5 is very remarkable, and but for 

 these remarks I should have remained ignorant of the existence of a living representative 

 of this variety of our fossil species, for no examples are preserved in the Kew Herbarium. 

 Prof. Newberry continues : — " 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. There is little 

 room for doubt, therefore, that during the Miocene age a species of Onoclea flourished in 

 the interior of our continent, of stronger habit than either of the living varieties, and 

 holding a middle position between them. This fact suggests the question, whether they 

 could not have been differentiated from it." 



" Varying, as the living Onoclea does, in the size, outline and nervation of the sterile 

 frond — from six inches to three feet in height, from a finely reticulated to an open, 

 dichotomous nervation ; from a bi-pinnate frond with remote, obovate pinnules to a 

 pinnate form with wave-margined pinnae and broadly alate rachis — it plainly includes 

 all the characters of the fossils before us, and I therefore find it impossible to separate 

 them." 



1 'Ann. Lyc. Nat. Hist. N.Y.,' vol. ix, p. 39, April, 1865. 



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