286 CONTRIBUTIONS FEOM THE NATIONAL HERBARIUM. 



15. HOLCUS L. 



Racemes reduced to 1 to 5 joints, borne on slender peduncles on the slender 

 branches of a compound panicle; rachis slender, tardily disjointing; spikelets 

 arranged as in Andropogon, the pedicellate spikelet usually sraminate, the sessile 

 spikelets awnless or with a deciduous awn. 



Plants perennial, with creeping rhizomes 1. H. halepensis. 



Plants annual 2. H. sorghum. 



1. Holcus halepensis L. Sp. PI. 1047. 1753. Johnson grass. 

 Andropogon halepensis Brot. Fl. Lusit. 1: 89. 1804. 



Sorghum halepensis Pers. Syn. PL 1: 101. 1805. 



A robust perennial with numerous stout rhizomes, flat scabrous-margined 

 blades, and a large open panicle of plump spikelets with deciduous awns. 



A weed in fields and waste places in the warmer parts of America ; introduced 

 from the Old World. Originally described from Syria. Found in all the large 

 islands and probably in most of the smaller ones. 



This species is described by Humboldt, Bonpland, and Kunth, 1 with Habana, 

 Cuba, given as locality, under the name "Andropogon avenaceus Schrad." This 

 is evidently a misprint for A. arundinaceus Willd., as described by Schrader. 2 

 In Cuba this is called " canuela " and " hierba de Don Carlos." 



2. Holcus sorghum L. Sp. PI. 1047. 1753. Sorghum or Sorgo. 

 Andropogon sorghum Brot. Fl. Lusit. 1: 88. 1804. 



Sorghum vulgare Pers. Syn. PI. 1: 101. 1805. 



Sorghum dora Griseb. Fl. Brit. W. Ind. 560. 1864. 



A large broad-leaved annual, with a compact panicle of turgid persistent 

 spikelets. 



Occasionally cultivated in the West Indies and sometimes spontaneous in 

 waste places or near fields. Widely cultivated in other parts of America and 

 in the Old World, whence originally described. In the English islands it is 

 often called " Guinea corn " ; in Cuba it is called " millo." 



2a. Holcus sorghum sudanensis (Piper) Hitchc. Proc. Biol. Soc. Washington 



29: 128. 1916. Sudan grass. 



Andropogon sorghum sudanensis Piper, Proc. Biol. Soc. Washington 28: 33. 



1915. 

 Resembling no. 1, but less robust and having no rhizomes. 

 Coming into cultivation in the West Indies in recent years and sparingly 

 escaped. Described from a cultivated specimen grown from seed from the 

 Sudan. 



Santo Domingo, Porto Rico, and St. Vincent. 



16. SORGHASTRUM Nash. 



Racemes arranged as in Holcus, the pedicellate spikelet wanting, the pedicel 

 only present; rachis flexuous, readily disjointing. 



Awn straight or slightly bent, not strongly spirally twisted at base, shorter than 

 the spikelet or sometimes a little longer 1. S. parvifiorum. 



Awn geniculate, strongly spirally twisted at base, about 3 times as long as the 

 spikelet 2. S. stipoides. 



x Nov. Gen. & Sp. 1: 189. 1816. 2 F1. Germ. 1: 237. 1806. 



