Jones: Flora of Illinois, 22. Gramineae 63 



2. Spikelets pubescent, 1-1.5 mm. long; blades 6-15 mm. wide; muddy banks 

 or in shallow water, s. and w. 111. Aug.-Oct. [P. re pens Berg.; P. mu- 

 cronatum Muhl.} P. fliiitans (Eli.) Kunth 



2. Spikelets glabrous, 2 mjn. long; blades 2-5 mm. wide; in ditches or along 



muddy or sandy shores, s. Ill P. dissectum L. 



1. Rachis narrow, less than 2 mm. broad; spikelets glabrous. 



3. Spikelets not more than 2 mm. long; plant often with 1 — several a.xillary 



peduncles from the upper sheath. 

 4. Spikelets orbicular; blades sparsely pilose and ciliate; sandy soil, road- 

 sides, etc. July-Sept P. stramineum Nash 



4. Spikelets oval or somewhat obovate; blades softly pubescent on both 



surfaces; moist sandy soil, throughout 111., except the n. part. July- 

 Sept. [P. rnuhlenbergii Nash] P. pubescens Muhl. 



3. Spikelets 2.8-3 mm. long; plant simple, without axillary peduncles from 

 the upper sheath. 



5. Spikelets orbicular, arranged singly in 2 rows; wet ground, chiefly in 



the s. half of the state. July-Sept P. circulare Nash 



5. Spikelets oval or slightly obovate, borne in pairs and appearing as if in 

 3 or 4 rows; ditches, rare, s. 111. Aug.-Sept. [P. pubiflorum var. 

 glabnim Vasey; P. laeviglume Scribn.} P. geminiim Nash 



61. Panicum L. 

 1. Spikelets glabrous. 



2. Spikelets 3 mm. or more in length. 



3. Plants glabrous, perennial, with rhizomes; panicle 15-50 cm. long; 

 spikelets 4-4.5 mm. long-pedicelled; roadsides and fields, common. 

 July-Sept. Switch Grass P. virgatum L. 



3. Plants pubescent. 



4. Spikelets 4-5 mm. long; panicles often drooping at maturity; waste 

 places; cult, and occasionally spontaneous; native of the Old 

 World. Broomcom Millet P. miliaceum L. 



4. Spikelets 3-3.8 mm. long, lanceoloid, pointed; panicles erect. 



5. Plants annual; panicles 10-30 cm. long; blades 2-5 mm. wide; 

 sandy soil, common. July-Oct P. flexile (Gatt.) Scribn. 



5. Plants perennial. 



6. Panicle loose, open, 20-50 cm. long; blades 6-10 mm. wide; 

 plants with long scaly rhizomes; along ditches, or in moist 

 soil, or woods, in the s. and w. parts of 111., extending northw. 



to Peoria and Henderson counties. July-Sept 



P. anceps Michx. 



6. Panicle 4-8 cm. long, not much exceeding the leaves, few- 

 flowered; blades 2-5 mm. wide; open woods. May-June 



P. depauperatum Muhl. 



2. Spikelets less than 3 mm. long. 

 7. Sheaths glabrous. 



8. First glume not m.ore than one fourth the length of the spikelets, 



