130 ME. G. BENTHAM ON GEAMINEJE. 



Old "World, chiefly in the northern hemisphere ; and scarcely any 

 species, except as introduced weeda or escapes from cultivation, 

 penetrate within the tropics. The twelve genera are readily 

 ranged in three distinct subtribes, and require but little comment 

 on the present occasion. 



The first subtribe, Triticew, comprises four genera, in which 

 the spikelets have three or more, or very rarely only one or two, 

 flowers, and are singly sessile at each notch of the rhachis. 



1. LoLiTJM, Linn., is at once distinguished from all others of 

 the tribe by the position of the flat spikelets with their edge 

 to the rhachis. Steudel enumerates twenty-two species ; most 

 authors reduce them to three or four, which run much into each 

 other. De Rouville published at Montpellier a detailed mono- 

 graph, in which he rejects all the old species and redivides the 

 genus into three primary and several subordinate races, to which 

 he gives new characters and new names, doing little but add to 

 the prevailing confusion. Two genera have been founded on in- 

 dividual species or forms — CroBpalium, Schrank, is the L. temulen- 

 tum, Linn., and .Arthrochortus, Lowe, is a Madeiran species or 

 variety very near to L. rigidum, Gaudin {L. strictum, Parlat.), 

 and to some varieties of L. temulentum. 



2. A GEOPTEUM, J. Gsertn. {Elytrigium, Desv.), contains about 

 twenty species, formerly regarded as congeners of the cultivated 

 Wheats, from which they differ much in habit and technically in 

 the lateral nerves of the flowering glumes connivent at the top 

 or confluent into the terminal awn. They are well distributed 

 into two sections : — 1. Agropyrum proper, mostly perennials, 

 with the spikelets more or less distant along the common pe- 

 duncle or rhachis, the outer empty glumes usually very unequal- 

 sided and not keeled. To this section belong the common A. re- 

 pens, A. junceutn, A. caninmn, and a few others. Sosgneria, 

 C. Koch, is, according to G-risebaoh, a species closely allied to 

 A. caninum. AnthosacJine, Steud., is the Australasian A. scabrum, 

 Beauv. {Festitca scalra, Labill.), which, with the closely allied 

 East-Indian A. semioostatum, Nees, and the Oriental A. longearis- 

 tatum, Boiss., differs from the commoner species in the denser 

 spikes and narrower glumes tapering into long awns at length 

 diverging. A. pectinatvm, Beauv., is an Australian species still 

 further connecting .4yropy>'jwre proper with JLremopyrum. 2. Ere- 

 mopyrum, Ledeb. {Cremopyrum, Schur, perhaps by a clerical 

 error, Costia, Willk.), mostly annuals, with the spikelets distichous 



