86 THE TRUE GRASSES. 



ft. Spikelets not in pairs at the nodes of the 

 branches. 

 I. Spikelets without empty glumes. 



1. Spikelets linear. Embryo as long as 



the fruit 83. Zizania. 



2. ? spikelets ovate or elliptical. Eni- 

 bryo many times smaller than the fruit. 

 * $ and ? spikelets in different pani- 

 cles, rarely in the same, and then the 

 $ spikelets terminal on each branch. 

 81. Luziola. 



** $ and ? spikelets in the same pani- 

 cle, the ? terminal, the $ at the 

 base of each branch. 82. Zizaniopsis. 

 II. Spikelets with two very small or bristle- 

 like empty glumes. . . 84. Potamophila. 

 B. Spikelets all $ . 



a. Spikelets arranged in panicles. 



a. Empty glumes two, short but distinct, awnless 

 (two additional rudimentary empty glumes in 

 Oryza}. 



I. Flowering glume and palea roundish in 

 section (but slightly compressed). 



85. Maltebrunia. 



II. Flowering glume and palea much com- 

 pressed laterally 86. Oryza. 



/?. Empty glumes two, awned, exceeding or slightly 

 shorter than the flowering glume. 

 * Empty glumes gradually tapering into awns. 



68. Achleena. 

 ** Empty glumes awned from a notch in the 



apex 89. Reynaudia. 



y. Empty glumes wanting or present only as 

 minute rudiments. 



I. Flowering glume awnless. . 87. Leersia. 

 II. Flowering glume awned. . 90. Hygroryza. 



b. Spikelets in a terminal, naked spike at whose apex 

 the ends of the awns of all the spikelets are fast- 

 ened together 93. Streptochseta. 



