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Pteris aquilina, and also differs from it in the pinnules which are 

 usually shorter, broader and closer, and in the frond which holds 

 its bipinnate character nearer to the summit. Fifty-three sheets 

 of this species were examined which shows its range to extend 

 from our southern border into British America, and from the 

 Rocky Mountains to the Pacific. Specimens from every State in 

 this area as well as those traversed by the Rocky Mountains, 

 have been seen. The same species appears to be found in various 

 parts of South America and the Old World, although some 

 refer the Old World specimens to another species. If we are to 

 have a separate genus for the species of Pteris with "a double 

 involucre" this would be called Pteridium lanuginosum (Bory). 



Pteris caudata L. {Pteris aqtiilina caudata (L.) Hook. 

 Sp. Fil. 2: 196. 1858. Pteridium aquilinum caudatum (L.) 

 Kuhn). This is a species nearly confined to the tropics which 

 extends into the warmer parts of the United States. It is char- 

 acterized by its height, narrow pinnules and pinnate branching. 

 Twelve feet is not an unusual height for this fern. The fronds 

 rise from a creeping rootstock, on a stout stipe. At a foot or 

 more above the earth, the first pair of pinnae are given off. 

 These are spreading, nearly horizontal but usually drooping at 

 the tips. The next pair are almost exact duplicates of the first, 

 but little smaller, and with the same drooping habit. These are 

 often at right angles to the first pair. In none of the many 

 specimens that I have seen, does the frond hint at the ternate 

 form of P. aquilina. The pinnae branch in every direction, 

 gradually decreasing to the half-drooping summit. The frond is 

 usually tripinnate, or with the pinnae again pinnatifid. The ter- 

 tiary pinnules or pinnae, are from a half to one inch long, and 

 from less than one to four lines wide, usually separated from each 

 other by from one to four times their width. Terminal pinnule 

 several times longer than the others. Frond gray green in color. 

 The forty-nine sheets of this species which I have seen show it to 

 be present in only California, Texas and Florida, the greatest 

 number from the latter State. In Mexico and the West Indies it 

 is abundant, and doubtless will be found to occur in most of the 

 Gulf States near the coast. Pteris escule?ita Forst. of the 

 tropics seems a mere variety of this, being distinguished by the 

 pinnules decurrent upon the mid-rib, at a sharp angle, giving it a 

 peculiar zigzag appearance. 



Pteris auuilina L. This is the common form in Eastern 

 America. It is the one described in all our text books, and may 



