Mb. e. BENIHAM ON SEAMINlSiE. 79 



in the larger genera there occur occasional exceptions more or 

 less decided, which prevent our taking any single one of them as 

 an absolute teat. The subtribe would include the following eight 

 genera, in the first five of which the fruiting glume is more or 

 less hardened or rigid as in Paniceae ; in the succeeding three it 

 is thinner, though still closely pressed on the grain. 



1. Aeistida, Linn., is now a genus of at least a hundred 

 species, abundant in all the warmer regions of the globe, but also 

 represented by a few species in Europe and temperate Asia, and 

 by several in North America. With few exceptions it is most 

 readily recognized by the long, fine, three-branched awns, the 

 lateral branches opposite and spreading. Doell adds to the 

 generic character three lodicules as in Stipa ; and Nees describes 

 three lodicules in some South-African species ; but all other 

 Agrostologists describe two only, and I have never found more 

 than that number. It is probable that both Nees and Doell 

 mistook for the third lodicule the palea, which in many species 

 is very thin and scarcely, if at all, larger than the lodicules. The 

 genus is divided into three fairly marked sections, which Beau- 

 vois, Nees, and some others have raised to the rank of genera. 

 In (1) Ghcetaria, Beauv., the flowering glume is continuous with 

 the awn without any articulation, and though much longer than 

 the empty glumes, and often much attenuated at the end, is 

 neither quite awn-like nor decidedly twisted below the branches. 

 Amongst its species, Curtopogon was proposed as a genus by 

 Beauvois for the North- American A. dichotoma, Mich., in which 

 the lateral branches of the awn, instead of diverging from the 

 central one, are short and erect at its sides, showing more or less 

 distinctly that they are continuations of the lateral nerves of the 

 glume. It is probable that this is the case throughout the genus, 

 only that the lateral nerves before they diverge are so closely con- 

 solidated with the central one as to be undistinguishable from it. 

 The genus OrtacJme was proposed by Nees for two or three 

 Mexican or Columbian plants, originally published by Kunth as 

 species of Streptachne, Br., and afterwards transferred by him to 

 Aristida, in which the lateral branches of the awn are very short, 

 sometimes minute or even quite obsolete, thus nearly connecting 

 the section Ghcetaria of Aristida with the section Aristella of 

 Stipa, but in the narrow base of the rhachilla, and some other 

 minor points, nearer to the former than to the latter. Ortachne 

 retorta, Nees (in Steud. Gram.), is probably a true Stipa. In 



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