78 ME. a. BENTHAM ON GKAMrtTEiE. 



Trinius, in his elaborate monograph of the tribe, divided it into 

 three primary groups or subtribes — Vilfete with the callus scarcely 

 prominent or quite obsolete, Agrostese with the callus globular, 

 and StipesB with the callus obconical. In this I feel unable to 

 follow him. In the first place he does not appear to have con- 

 sidered what the so-called callus really is. It is not, as the name 

 would suggest, an appendage to the base of the flowering glume, 

 or, as he would have termed it, to the flower, but only the upper 

 or principal part of the rhachilla or axis of the spikelet, to which 

 the glume and its enclosed flower are attached, and which breaks 

 ofi' immediately above the persistent empty glumes. Its shape 

 depends on the distance at which the flowering glume is attached 

 above the empty ones, a distance very variable throughout the 

 Order. And although the long or the short interval may be 

 more prevalent or even constant in some genera, yet I have never 

 found the variations so precise as to be defined by actual measure- 

 ment, and the species are numerous, even in Stipa itself, where 

 it is doubtful whether we should call it long or short. It is 

 sometimes a useful accessory character, but, I believe, never 

 positive enough to be regarded as subtribual. It is true that no 

 other simple absolute character has yet been proposed for the 

 subdivision of the tribe ; but we are obliged, here as elsewhere, 

 to take a combination of characters, to each of which an occa- 

 sional exception must be allowed. Acting on this principle, we 

 might, whilst following in many respects the arrangements of 

 Kunth and others, admit thirty-seven genera of Agrostes, dis- 

 tributed in four fairly natural subtribes, all four of wide geogra- 

 phical range, but chiefly in temperate regions, the tropical species 

 mostly confined to mountain districts, and no genus, except a few 

 monotypic ones, exclusively tropical. 



Our first subtribe, Stipeje, is the long-established one of that 

 name, slightly extended so as to include Oryzopsis, Muelilen- 

 lergia, and their immediate allies, the close connexion of which 

 with Stipa has been frequently suggested. The subtribe thus 

 formed would be characterized by the paniculate inflorescence 

 not condensed into the cylindrical spike of Phleoidese, by the 

 rhachilla of the spikelet not produced beyond the flower except 

 in the single species of Brachyelytrum, by the awn of the flowering 

 glume terminal, not dorsal as in Euagrostea;, and especially by 

 the grain being very closely enveloped in the fruiting glume. 

 In the majority of species these characters are well marked ; but 



