with Be&criptions of N< w Sj>. ci< 8 of Fossil Plants. 



unkeeled, flag-like leaves, marked by. numerous lougitudinal 

 nerves, of which there are eight or nine more Btrongly marked. 

 and between these about seven much finer, couuected bv alter 

 nate cross-bars. No keel is shown in any of these fragments. 

 In general structure these leaves closely resemble th. >.-e of /'. 

 Oeningensis, Heer (Flor. Tert. Ilelvet i. S. »!4. Taf. xxh : 

 but the material is not sufficient to determine whether our 

 species is identical with that. 



Formation and Locality. Fort Union, Dacotah, (Dr. Har- 

 den.) 



Onoclea seiisibilis. L. 



Frond pinnate, large; pinnae, lanceolate in outline, with waved 

 margins, more or less deeply-lobed or pinnatitid, connate at their 

 bases, forming a broad wing on the rachis of the frond ; nervation 

 strongly marked, more or less reticulated, the nerve of each lobe or 

 pinnule springing from a common trunk having a dendroid form 

 with waving branches, which often unite to form elongated litcuncB, 

 of which the largest border the rachis of the pinna on either - 

 and are formed by the nerve branches of each lobe r< aching ov< r 

 and touching, or closely approaching, the base of the nervation of 

 the next superior lobe or pinnule. 



The collection of Dr. Ilayden contains a great number 

 examples of this beautiful fern, showing the upper and under 

 surface of the frond, the variation of form of the pinna of dif- 

 ferent fronds, and different parts of the Bame frond. 



The robust habit of this plant, the Btrong, waved and reticu- 

 lated nervation and broadly winged rachis, which Bcem to di* 

 tinguish it at a glance from all known fossil Bpeci 

 a comparison with some of the strong--,-,, win- tropical 

 and it was only after a laborious examination efall the 

 of exotic ferns contained in the licit. aria to which I bad I 

 or described by authors, that I was led to turn u, 



home. 

 The common form of Onoclea sensibilis growa abundantly in 



all parts of our country, and ifl one of the first plant! 



