20 



THE GENUS PANICUM IN THE UNITED STATES. 



This genus is one of great difficulty to the student, aud the present 

 monograph, it is hoped, will be of essential benefit in the prosecution 



of botanical investigation. 



Panicum, Linn. 



Spikelets with one perfect terminal flower, and usually a second one 

 which is male only or rudimentary. Outer empty glumes two, one of 

 which is smaller than the other, often very small, or rarely wanting, 

 membranaceous. The glume of the perfect flower with its palet are 

 usually of a coriaceous texture, and obtuse or obtusish. The second 

 flower, when present, is membranaceous. Inflorescence spicate or pan 

 iculate. 



Section 1. — Digitaria.— Panicles of several spikes or spike-like 

 branches, which are digitate or approximate at the top of the culm ; 

 spikelets usually small and in alternate pairs along one side of the flat- 

 tened rhachis, one sessile and one short pedicelled; empty glumes two, 

 or sometimes three, the lower one then being minute. 



1. P. glabrum, Gaud. 



2. P. sanguinale, Linn. 



3. P. flliforme, Linn. 



4. P. serotinum, Trin. 



Section II. — Trichachne. — Spikelets densely silky hairy, or fringed 

 with long hairs, sessile or short-pedicelled, in pairs or clustered along 

 the rhachis of the numerous simple, erect, spikes or branches of the pan- 

 icle, acute ; lower glume very minute. 



5. P. leucophoeum, S. B. K. 



6. P. lachnanthum, Torr. 



Section III. — Subspicaia. — Panicle linear or narrow, the branches 

 short, sessile, erect or appressed, or the apex spicate. 

 Branches densely floivered : 



7. P. paspaloides. Pers. 



8. P. Curtisii, Chap. 



9. P. obtusum, H. B. K. 



10. P. reticulatum, Torr. 



11. P. Texanum, Buclrf. 

 Branches lax floiccred : 



12. P. Chapmani, Vasey. 



13. P. Reverchoni, Vasey. 



14. P. subspicatum, Vasey. 



15. P. stenodes, Gris. 



Section IV. — Platyphylla. — Panicle of few (three to six), simple, 

 mostly sessile, spreading branches, the spikelets sessile in two rows on 



