THE FERNS OF NICARAGUA. 



143 



A. intermedium Swartz, — Hook., Sp. Fil., vol. II, p. 25; Eaton, Fil. Wr. et 



Fend., p. 202; Hook, and Bak., Syn. Fil., p. 116; Smith, Hist. Fil., p. 



275; Smith, Ferns, Brit, and For., p. 184; Hemsl., Biol. Cent. Am., vol. 



in, p. 609; Bak., Jour, of Bot., vol. xxn, p. 362 (from Costa Rica); 



Hitch., PI. Bah., p. 152. 

 A. triangulaium Kaulf., — Hook., Sp. Fil., vol. 11, p. 26. 

 A. fovearum Raddi, — Smith, Hist. Fil., p. 275; Smith, Ferns, Brit, and 



For., p. 184. 1 



The fine series of Nicaragua specimens shows a great 

 variation in division. The fronds are about equally divided 

 between forms with simple pinnae, and those with the lower 

 one to three pairs of pinnae compound. 



A perfect series connects the extremes. 3 In some specimens 

 one basal pinna only is somewhat compound, while in others 

 there are three lateral pairs of compound pinnae each with 8 to 

 10 pairs of pinnules, and between them is an unbroken series of 

 intermediate forms. The once-pinnate fronds have the pinnae 

 larger than the pinnules of the bi-pinnate forms, but in the in- 

 termediate forms with small compound basal pinnae, the pin- 

 nules of what may be regarded as the terminal pinna are 

 large, being like those of some of the once-pinnate fronds. 



The roostock is long, slender, about one line in thickness, 

 creeping, and covered with small, lance-linear, acuminate, 

 brown, appressed scales, some of them hair-like. The stipes 

 are ordinarily less than one-half an inch apart. The ultimate 

 divisions vary from broadly obtuse to rather narrowly acu- 

 minate. The sterile pinnae are sometimes cleft. 



It will be observed that at least three forms, ordinarily rec- 

 ognized as distinct species, are here grouped together. The 

 simply pinnate forms are usually classed as A. obliquum,* and 

 A. kaulf ussii, A and the compound forms as A. intermedium. 5 



1 As additional references for A. obliquum Willd., add: Lieb., Mex. Breg., 

 p. in ; Smith, Ferns, Brit, and For., p. 183. 



Under A. kaulf ussii add: Hitch., PI. Bah., p. J52. 



8 After the printing of the form immediately preceding these pages, the 

 author decided to still more fully illustrate the forms herein grouped to- 

 gether, and added fig. 2 to pi. v, and plates vn and vm. Reference should 

 have been made to these on the preceding page. 



3 PI. vi, figs. 4 and 5. 



4 PI. v, figs. 5 and 11, and pi. vi., figs. 1 and 2. 



5 PI. vm, figs. 1 and 2 are extreme forms; pi. v, figs. 6, 8 and 9, pi. vi> 



IV— 11 L 



