GRASSES OF IOWA. 



PANICUM. 



Panicum L. Sp. PI. 55. 1753. Endlicher. Gen. PI. S3. Bentham & 

 Hooker. Gen. PI. 3: 1100. Hackel in Engler & Prantl. Nat. Pflanz. Fam. 

 II. 2: 35. f. 26-27-2S. Scribner Bull. U.S. Dept Agrl. 20: 37. Vasey. Contr. 

 U. S. Nat. Herb. 3: 22. Thalasium Spreng. Syst. Cur. Post. 22: 30. Pani- 

 cum as here defined includes Digitaria. Scop. PI. Carn. 1: 52. 1772. (ed. 2.) 

 which equals Syntherisma. Walt. Fl. Car. 76. 1788. and Echinochloa. 

 Beauv. Agrost. 53: pi. 11. f. 11. Reichb. lc. PI. Germ. PI. 39. 



Spikelets jointed upon the pedicels, ovate, panicled, racemed, or 

 sometimes spiked, not involucrate, with one perfect and sometimes a 

 second lower rudimentary or staminate flower. Glumes 4, but the 

 lower one usually short or minute (rarely wanting), and the 

 third empty or sterile, membranaceo-herbaceous. Upper flower perfect, 

 closed, coriaceous or cartilaginous, usually flatfish, parallel with the 

 glumes, awnless, enclosing the free and grooveless grain. Stamens 3. 

 Stigmas plumose, usually purple. (An ancient Latin name of the 

 Italian Millet, Panicum, now Setaria Italica of uncertain origin and 

 meaning.) 



There are about 300 species of Panicum found in the tropical and 

 subtropical regions of both hemispheres. A comparatively small number 

 occurring in temperate regions. Bentham & Hooker give the number 

 of species between 250 and 280 but the number has considerably increased 

 since the publication of their Genera Plantarum. The Hackel estimate 

 of 300 is probably a conservative one. Of the 60 species in Australia 

 several are common to Africa, Asia and America. 



KEY TO THE SPECIES OP PANICUM. 



I. Spikelets in one-sided racemes. 



1 . Racemes scattered (Echinochloa) . 



A. Sheaths glabrous. 



a. Spikelets awned P. Crus %alli} 



b. Spikelets awnless P. Crus-galli var muticum. 1 



B. Sheaths, at least the lower ones,papillose hirsute P. Walteri* 



2. Racemes slender, digitate or whorled, sometimes in pairs. (Syn- 



therisma. ) 



A. Rachis of the racemes with the angles wingless. P. filiforme.' 1 



B. Rachis of the raceme with the lateral angles broadly winged. 



a. Sheaths and leaves smooth and glabrous. . .P. glabrum.* 



b. Sheaths and leaves papillose hirsute P. s (inguinale." 



II. Spikelets in a true panicle. (Eupanicum.) 



1. Basal and culm leaves similar, usually elongated. 



A. Culms branched (at least al matur'ty) , no scaly root-stocks, 

 a. Sheaths very pubescent. 



aa. Spikelets lanceolate, 3 mm. long or less. 



t Annual, pedicels usually from two to three times 

 the length of spikelets. 



