CHAPTER XXXI 



PLAGIOGYRIACEAE 



The single genus included in this family has by reason of its curiously 

 mixed characters been greatly misunderstood. The outstanding feature is 

 the presence of an oblique annulus in a Fern having the habit of a Lomaria. 

 So long as those external features which constitute "habit" dominated 

 classification such misunderstandings were natural. But when so pronounced 

 a feature as an oblique annulus is combined with a relatively primitive 

 anatomy and with dermal hairs, it is high time to reconsider the value of 

 habit as a guide. 



The genus Plagiogyria was first distinguished by Kunze {Bot. Zeit. p. 

 867, 1849), who regarded it as a section of Lomaria. Later it was the 

 subject of special examination by Mettenius {Farngattwigen, ii, Frankfurt, 

 1858), who on the ground of the oblique annulus placed it with the Cyathe- 

 aceae. But Sir W. Hooker, following Kunze, still retained it with Lomaria, 

 where it appears in the Synopsis Filicum, 1874, p. 182. Christ {Fanikrdiiter, 

 pp. 6, 175), ranks it as a substantive genus with the Pterideae, placing it 

 between Pteris and Blechniim. Diels ranks it in that rather incongruous 

 group, the Pterideae-Cheilanthinae {Natiirl. Pflanzenfam. i, 4, p. 281). In 

 Christensen's Index it appears as the last genus of the Cheilanthinae, in 

 close relation with Cryptogramme and Llavea (p. xliii). 



There is no doubt that the sporangium with its oblique annulus must be 

 given full weight, but the general characters of this remarkable genus must 

 also be taken into account before any final position can be assigned to it. 

 The fact that Plagiogyria alone of described Ferns combines the oblique 

 annulus of some Simplices and of the Gradatae, with certain general 

 characters of the Mixtae, at once commands attention and suggests for it 

 a position as a synthetic type. As at present described there are eleven 

 species: two are found in Central America, and the rest are Eastern, widely 

 spread in the Malayan region. 



These Ferns have an erect, radial woody stem, covered by the crowded 

 leaf-bases, and giving the effect of a stunted tree-fern: in fact they have the 

 habit seen in the Osmundaceae. Occasionally the axis bifurcates, particularly 

 in P. semicordata Baker: but this has not been seen in P. pycnopJiylla Kunze, 

 a species which, however, bears stolons. These vary in length, taking at 

 first a horizontal course as thin runners bearing scale-leaves: but sooner or 

 later they expand at the apex into a massive upright trunk with dense 

 foliage. There is reason to regard the dichotomy and the formation of 

 stolons as complementary modes of branching: the latter may even be 



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