266 BULLETIN 772, U. S. DEPARTMENT OF AGRICULTURE. 



Arthraxon Beauv., Ess. Agrost. 111. 1812. Type species, A. 

 ciliaris Beauv. This Old World genus is represented in North 

 America by A. qiwrtwiwms (A. Eich.) Nash, introduced into Ja- 

 maica and Guadaloupe, and by A. ciliaris cryptatherus Hack., estab- 

 lished in the vicinity of Washington, D. C. The latter is a creeping 

 slender grass with thin cordate-lanceolate blades, the inflorescence 

 of several slender racemes in a cluster. 



133. HOLCUS L. 

 (SorgJmm Pers.) 



Spikelets in pairs, one sessile and fertile, the other pedicellate, 

 sterile but well developed, usually staminate, the terminal sessile 

 spikelet with two pedicellate spikelets. 



Annual or perennial, tall or moderately tall grasses, with flat 

 blades and terminal panicles of 1 to 5 jointed tardily disarticulating 

 racemes. Species about six, one Mexican, the others in the Old 

 World ; two cultivated or introduced into America. 



Type species: Holcus sorghum L. 



Holcus L., Sp. PI. 1047, 1753; Gen. PL, ed. 5, 469. 1754. Linnreus describes 

 seven species, H. sorghum, H. saccharatus, H. halepensis, H. lanatus, H. odo- 

 ratus, H. laxus, and H. striatus. The selection of the type species is of 

 particular importance in this genus, because it affects the generic name of 

 the group containing the cultivated sorghums. The first three of the original 

 seven species were segregated from the others in 1763 by Adanson, who applied 

 to them the old name sorghum, used by Bauhin and other pre-Linnsean authors 

 for the cultivated sorghums. This name was accepted by most of those subse- 

 quent authors who recognized the group as a genus distinct from Andropogon, 

 and as a subgeneric name by those who held it to be a subgenus of Andropogon. 

 Of the remaining four of the original seven species of Holcus all but H. lana- 

 tus were early assigned to other genera, leaving H. lanatus in possession of the 

 generic name and in effect making this residual species the type of the genus. 

 Linnaeus, however, in all the editions of the Genera Plantarum and in the 

 Hortus Cliffortianus and the Hortus Upsaliensis used the name Holcus for 

 sorghum only. The description and the synonymy in all cases apply only to the 

 first three of the seven species included in the Species Plantarum. Moreover, in 

 all the editions of the Genera Plantarum Linnaeus cites " Sorgum Mich." While 

 Micheli 1 gives no description or figure of the genus, we know from Bauhin 

 and others that Sorgum or Sorghum was in common use for the group in 

 question. Linna?us uses the old name Sorghum for the trivial or specific name 

 of the first species, and cites Sorghum of Bauhin as a synonym. It is clear 

 that the Holcus of Linna?us is the old Sorghum, the other four diverse species 

 (which do not agree with the generic descriptions in any of the works cited), 

 evidently being appended for want of a place to put them. According to the 

 American Code the genera of Lirmseus's Species Plantarum are to be typified 

 through citations given in his Genera Plantarum of 1754. The reference to 

 Micheli, the use of sorghum as a specific name, and the descriptions all point 

 to H. sorghum as the type of the genus Holcus. Holcus lanatus is now referred 

 to Notholcus, H. odoratus to Torresia (Hierochloe, Savastana), H. laxus to 

 Uniola, and H. striatus to Sacciolepis. By many authors the genus Holcus as 

 here understood is included under Andropogon. 



Blumenbachia Koel., Descr. Gram. 28. 1802. A single species, " B. halep- 

 pensis." based on " Holcus Haleppensis Linn." is included. 



Sorghum Pers., Syn. PI. 1 : 101. 1805. Four species are included. Holcus 

 sorghum L., upon which . vulgare Pers. is based, is taken as the type. 



. Plant. Gen. 35. 1729. 



