52 



POACEAE 



TRIBE IX. AVENEAE. 



Spikelets readily deciduous as a whole. 



Spikelets with the empty scales persistent, the flowering scales deciduous. 

 Spikelets 2-flowered : rachilla not prolonged. 



Spikelfts 2-many-flowered : rachilla extending beyond the upper flower. 

 Flowering scale awned below the teeth. 

 Flowers all perfect. 



Grain free, unfurrowed : spikelets less than 1 cm. long. 



Flowering scales erose-toothed or shortly 2-lobed at the apex. 

 Flowering scales cleft or ^-toothed, the teeth extending into 

 awns. 



68. HOLCUS. 



69. AIRA. 



70. DESCHAMPSIA. 



71. TKISETUM. 



Grain furrowed, adherent to the scale : spikelets exceeding 1 cm. 



in length. 72. AVENA. 



Flowers different, the upper perfect, the lower staminate and with its 



scale strongly awned. 73. ARRHENATHERUM. 



Flowering scales awned between their usually awned teeth. 



TRIBE X. CHLORIDEAE. 



A. Spikelets with perfect flowers. 

 Spikelets deciduous as a whole. 



Spikelets with at least the empty scales persistent. 

 Spikelets with one perfect flower. 

 No scales above the flowering scale. 

 Spikes 2-6, digitate. 



Spikes numerous, arranged along a common axis. 

 1-several scales above the flower. 

 Empty scales 4. 

 Empty scales 2. 



Spikes in whorls or closely approximate. 



Flowering scales with a single awn or awnless. 



Second empty scale acute : awn of flowering scales usually 



long. 

 Second empty scale truncate or 2-toothed : flowering scales 



awnless or awn-pointed. 

 Flowering scales with three awns. 

 Spikes scattered. 



Spikelets scattered or distant. 

 Spikelets crowded. 



Spikes generally 4 or less, rarely as many as 8, long : spike- 

 lets numerous, exceeding 12. 



Spikes often numerous, short : spikelets few, less than 12. 

 Rachis of the spikes with manifest internodes. 



Spikelets broad, crowded ; internodes of the rachis 

 short : rachilla terminated by a 3-awned scale, 

 or sometimes reduced to 3 weak awns. 

 Spikelets very narrow, scattered : internodes of the 

 rachis at least % as long as the spikelets: ra- 

 chilla terminated by 3 stout awns. 

 Rachis with the internodes so short that the spikelets 



appear clustered. 

 Spikelets with 2-3 perfect flowers. 



Spikes commonly digitate ; spikelets crowded. 

 Spikes with terminal spikelets. 

 Spikes with the rachis extending beyond the spikelets in a manifest 



point. 

 Spikes distant : spikelets alternate. 



Spikelets small, numerous and crowded : scales thin. 

 Spikelets large, few and distant : scales firm and thick. 



B. Spikelets dioecious, those of the two sexes very dissimilar. 



74. DANTHONIA. 



76. SPARTINA. 



75. CAPRIOLA. 



82. SCHEDONNARDUS. 



77. CAMPULOSUS. 



78. CHLORIS. 



79. EUSTACHYS. 



80. TRICHLORIS. 



81. GYMNOPOGON. 

 83. BOUTELOUA. 



84. ATHEROPOGON. 



85. TRIATHERA. 



86. POLYODON. 



87. ELEUSINE. 



88. DACTYLOCTENIUM. 



89. LEPTOCHLOA. 



90. ACAMPTOCLADOS. 



91. BULBILIS. 



TRIBE XI. FESTUCEAE. 



Flowering scales many-cleft into awn-like divisions. 92. PAPPOPHORUM. 



Flowering scales entire, or at most 2-lobed. 



Hairs on the rachilla or flowering scale very long and enclosing the latter : 



tall reed-like grasses. 



Flowering scales hairy : rachilla glabrous. 95. ARUNDO. 



Flowering scales glabrous : rachilla hairy. 96. PHRAGMITES. 



Hairs, if any, on the rachilla or flowering scales shorter than the scale : 



grasses of lower stature. 

 Stigmas barbellate, on elongated styles. 



Spikelets dioecious, single, concealed in the heath-like leaves. 93. MONANTHOCHLOE. 



Spikelets perfect, commonly in 3's, in the axils of stiff spinescent leaves. 94. MUNROA. 

 Stigmas plumose, sessile or on a short style. 



Flowering scale 1-3-nerved, or rarely with faint additional interme- 

 diate nerves. 

 Flowering scales membranous : seed not beaked nor exserted from 



the scale. 

 Lateral nerves of the flowering scale pilose. 



Internodes of the rachilla long, the deeply 2-lobed flowering 



scales attached by a long pointed callus. 99. TRIPLASIS. 



Internodes of the rachilla and the blunt callus of the flower- 

 ing scale short. 



Inflorescence simple or compound, contracted or open, the 

 spikelets on pedicels of varying length. 



