ANALYSIS OF SPECIMENS. 23 



But little practice will be required to gain familiarity 

 in thus analyzing the flowers of the grasses. 



1. Spikelets with but one flower, ^ 2 



1. Spikelets with two ox- more flowers, 26 



2. Flowers arranged in panicles 3 



2. Flowers in spikes 16 



3. With awns 4 



3. Without awns, 12 



4. Glumes large, 5 



4. Glumes minute, unequal, one hardly perceptible 11 



4. Glumes none, grass aquatic, 2 Zizania. 



5. Without abortive rudiments, 6 



5. With an abortive rudiment of a second flower, 52 Holcus. 



6. Palese two, . . . 7 



6. Paleae three, upper awned flowers polygamous, . 65 Sorghum. 



7. Palea with one awn, 8 



7. Lower palea with three twisted awns, 15 Aristida. 



8. Paleae cartilaginous or gristly, 9 



8. Paleae herbaceous 10 



8. Paleae membranaceous, panicle open, 7 Agrostis. 



8. Paleae membranaceous, panicle contracted, . . .8 Polypogon. 

 9. Flowers sessile, or joined to the stem at the base, . . 13 Oryzopsis. 



9. Flowers stipitate, fruit black, 14 Stipa. 



10. Flowers naked, with one stamen 9 Cinna. 



10. Flowers hairy, stamens three, 12 Calamagrostis. 



11. Stamens three, 10 Muhlenbergia. 



11. Stamens two, 11 Brachyelytrum. 



12. Glumes two 13 



12. Glumes none, leaves rough from the end backwards, 1 Leersia. 



13. Paleae membranaceous, 14 



13. Palese leathery, spikelets all cauline 56 Milium. 



13. Palese leathery, fertile spikelets radical, .... 57 Amphicarpon. 



14. Fruit coated, or covered with a husk, 15 



14. Fruit naked, 6 Sporobolus. 



15. Flowers stalked 7 Agrostis. 



15. Flowers sessile, 5 Vilfa. 



16. Flowers awned, 17 



16. Flowers without awns, . 22 



17. Spikes solitary, 18 



17. Spikes many, awnless, unilateral, paleae cartilaginous, 59 Panicum. 



17. Spikelets two, fertile, 63 Erianthus. 



17. Spikes two, polygamous, sterile flowers bearded, . . 64 Andropogon. 



18. Spikes simple, or nearly so, 19 



18. Spikes paniculate, or lobed, 21 



