FLORA OF ADEN. 
85f 
with 2 heteromorphous florets* the upper hermaphrodite, the lower 
male or barren ; rhachilla not continued beyond the upper floret. 
Tribe 1. Andropogoneae. Spikelets usually in pairs, one 
sessile, the other pedicelled, rarely 3-nate or solitary on the 
axes of variously arranged, often spikelike, racemes. Glumes 
more or less rigid and firmer than the valves, and the lower 
always longer than the florets. Valves membranous, often 
hyaline, that of the upper floret generally awned or reduced 
to an awn . ........ 1. Andropogon. 
Tribe 2. Paniceae. Spikelets in usually continuous spikes, 
racemes or panicles. Glumes herbaceous, or membranous, 
the lower smaller, very small or suppressed. Lower valve 
generally resembling the glumes in structure and nervation, 
the upper firmer, at length rigid, often chartaceous to 
crustaceous, awnless, very rarely mucronate. 
A. Mature spikelets persistent on their pedicels, 
surrounded singly or in clusters by an involucel of 
naked or plumose bristles or spines which fall along 
with the spikelets ...... 2. Pennisetum. 
B, Mature spikelets falling entire and singly from the 
tips of their pedicels : 
Spikelets subtended by an involucel of bristles 
Spikelets not subtended by bristles : 
Fruiting valve rigidly membranous 
Fruiting valve subchartaceous to crustaceous : 
Lower involucral glume distinct . 
Lower involucral glume absent or minute : 
Spikelets not thickened at the base . , 
Spikele ts thickened at the base . • . 
3. Setaria. 
4. Tricholsena. 
5. Panicum. 
6. Digitaria. 
7. Eriochloa. 
Series II. Mature spikelets breaking up, leaving the persistent or 
subpersistent glumes on the pedicel, or if falling entire, then not consist- 
ing of 2 heteromorphous florets as in Series I. 
Tribe 3. Stipeae. Floret 1. Rhachilla not produced 
beyond the upper floral glume which is bisexual, hardened 
when mature, tightly enveloping the fruit. Nerves joining 
or closely approaching at the tip .... . 8. Arrietida. 
Tribe 4. Sporoboleae. Involucral and floral glumes very 
similar. Floret 1. Rhachilla not (or rarely) produced 
beyond the floret. Upper floral glume membranous, acute 
or obtuse, not changed when ripe, 1-or more or less 3-nerved, 
awnless, usually olive-green or grey 5 side-nerves, if present, 
delicate, evanescent above ...... 9. Sporoholus. 
