KEY. 207 



560. Inflorescence strictly terminal ; the few-flowered 

 spikes crowded in a leafy-iuvolucrate head. Perianth none. 

 Style 2-cleft. Bracts colored. Achenium truncate at the 

 summit, transversely wrinkled, 



Dichromena leucocephala, Mx. 

 Gr. T. IV. 



Inflorescence both terminal and axillary 561 



561. Achenium beaked with the dilated, persistent style, 

 or its bulbous base. Perianth of bristles, or none. Stems 

 leafy 562 



Achenium not beaked, corky, or only pointed at the 

 top. Perianth none. Style 3-cleft. Stamens 2. Spikes 

 clustered in heads, 3-8 together on 2-4 peduncles. Culm 

 obscurely 3-cornered. Cladium mariscoides, Torr. 



Gr. T. V. 



563. Perianth of 5-12 bristles, rarely wanting 563 



Perianth none. Stamens 2. Spikes terete, ovoid, 

 cymose. Psilocarya scirpoides, Torr. 



Gr. T. IV. 



563. Style 2-cleft. Achenium tubercled with the base 

 of the style. Bristles 6-12. Spikelels few-flowered, ovate, 

 the scales loosely imbricated. Stem 3-sided. 



Gr. T. IV. Rhynchospora. 



Style simple, entire crowning the achenium as an 

 awned beak. Spikelets 2- to 5-flowered, one flower perfect, 

 lower ones staminate. Bristles 5 or 6. 



Gr. T. IV. OeratoschcBnus. 



564. (539.) True grasses. Perianth a pair of small Jrac^s 

 {c2i\\Q(i palem, pales, oy perianth, R. Br.), enclosing each par- 

 ticular flower, which is furnished also with 2 or 3 minute, hy- 

 pogynous scales (squamulse). Another pair of bracts (glumes 

 or calyx, L.) include 1, 2, several, or many flowers, forming 

 thus 1-, 2-, several-, or many-flowered spikelets, which are 

 collected into spikes or panicles. Stamens 3 (rarely 1, 2, or 

 6). Styles 2 (rarely 1). Stem usually hollow and closed 

 at the joints (culm), with alternate, 2-ranked leaves, their 

 sheaths split on the side opposite the blade, or rarely not 



