4" Later Extinct Floras of North. America, 



by the youthful botanist. Iu tins 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 retic- 

 ulated. By this I was at first misled, but in examining Dr. 

 Torrey'a var. obtusildbata^ 1 found in some specimens the exact 

 counterpart of our fossil in the lobation of the pinnae and nerva- 

 tion. The gradation of characters in this variety is very great 

 and interesting. In some specimens we have a distinctly bi- 

 pinnate 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 pinna? deeply lobed, and precisely the nerva- 

 tion of the fossil. Even in the common form the nervation is 

 similar in plan, and the elongated spaces, destitute of nerval 

 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 Mi- 

 ocene age a species of Onoclea flourished in the interior of our 

 continent, of stronger habil than either of the living varieties, 

 and holding a middle position between them. This fact sug- 

 gests the question, whether they could not have been differenti- 

 ated from it. 



Varying, as the living Onoclea does, in the size, outline, and 

 nervation of the Bterile frond — from six inches to three feel in 

 height, from a finely reticulated to an open, dichotomous nerva- 

 tion : from a hi-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. 



What ha- been predicated of this Bpecies has been based on 



observations of the sterile frond only. No fertile frond has vet 



ii found, and since in 0. sensibilis, var. ootusUobata, the 



"sterile" frond i- Bometimes fr a it-bearing, we may find that Mich 



