A«il{()STII»K.K. 1H:> 



T 



TuiHK VIII.— AOROSTIDEiE. 



Spikclcts usually coutuiniiix 1 luTt'ocit n«)wer each, racliilla 

 Hoiiu'tiiucs prolon^'iMJ bcyoiid tlu> paU'U. Kinpty jjluinos tj (none iti 

 ('nhaiilliiis, \ in rtoiiu' spocit's of S/itiro/ni/iis and Miililvulivri/iti), 

 usually iw lonj; us tlu' lloral «;lunu' or loiijrer; paU>a (wautiiij; in 

 MdjirrnfHs aiul some spccit's of Ajiroslis) S-iutvim! or ncrveli'ss 

 (l-iHTVi'd in ('iiin(i). (Jrain not furrowed, embryo small. 



This lariji' tribe is one of the most iliHicult \*> cireuniscribe satis- 

 factorily, or to divide into delinite ^jjenera. 'i'lieir jreneral charaeter 

 is to have a single flower in each spikelet. either terniinal or with a 

 slijjht bristle-likt' continuation of the ruchilla. The sin^rle (lower in 

 the spikeli't which separates the tribe from the following ones is 

 not so positive a character, a-s it occurs also in one<,'enusof Aveiuw, 

 in a few genera of Chloridea*. and occasionallv in Kestucea'. 



Trillins divided this triiio into three sul>tribes: Vilfeiv. with the 

 callus scarcely ]>roininent or oltsolete: Agrostea'. with the callus 

 globular; and Stipea*. with the callus ol)coiiical. lint the callus is 

 not an appendage to the Ijase of the lloral glume, as he would have 

 termed it. but only the upper jjart of the racliilla. to which the glume 

 and the enclosed floret are attached. Its shape depends on the dis- 

 tance at which the lloral glume is attache(l above the emi)ty ones, a 

 distance very variable throughout the Order. The length of the 

 joint of the raehilla ;s a useful chari>cter, but never ranks as sub- 

 tribal. 



A. Floral glume firmer than the empty glumes and very closely en- 

 veloping the grain. 



u. Spikelets each containing 1 perfect flower (b) 



b. Floral glume entire, bearing a terniinal ;}-brancluMl 

 awn. the lateral branches often very short or some- 

 times obsolete 45 



b. Floral glume 3-toothed, awn usually simple. 



twisted and bent (c) 



e. Lodicules usually 3. floral glume ai;d palea be- 

 coming very hard (d) 



