170 A TEXT-BOOK OF GRASSES 



are arranged in a large compound panicle. Several species 

 of this genus* furnish volatile essential oils and some are 

 cultivated for this purpose. The most common cultivated 

 species, both from India, are citronella-grass, C. Nardus 

 (L.) Rendle, and lemon-grass, C. citratus (DC.) Stapf. 



210. Holcus L. — Racemes reduced to the terminal 

 joint which consists of a fertile spikelet and a pair of 

 staminate spikelets, these racemes or groups arranged in 

 panicles. One species, H. halepensis L. (Fig. 17), the well- 

 known Johnson-grass, a native of the Old World, is now 

 naturalized in America. This is a valuable forage-grass 

 but on account of its tendency to spread in cultivated 

 fields and the difficulty with which it is eradicated it can- 

 not be recommended. It is a coarse perennial with creep- 

 ing rhizomes. The other important species of this genus is 

 sorghum (H. Sorghum L.), a tall coarse annual, not found 

 in the wild state but thought to be derived from the pre- 

 ceding species. There are many varieties cultivated for 

 various purposes,! the sugar sorghum, or saccharine sor- 

 ghum, for its juice, from which sugar and syrup are ob- 

 tained, the forage sorghum, often called "cane" on the 

 Great Plains, grown for forage, kafir, grown for forage 

 and the seed, broom-corn for the stiff branches of the 

 inflorescence, and durra, milo, Egj^tian com, etc., for 

 forage and seed. Many other varieties are cultivated in 

 Africa and Asia. In some countries it is called millet. 



The genus Holcus has been known as Sorghum and 

 has been included by many under Andropogon. The 

 names of the 2 species mentioned appear in books as 

 Sorghum halepense (L.) Pers. or Andropogon halepensis (L.) 



*For a discussion of this subject, see O. Stapf, "Oil Grasses of India and 

 Ceylon" (Kew Bull. Misc. Inf. 8: 297. 1906). 



tSee Ball, "History and Distribution of Sorghum" (U. S. Dept. Agric. Bur. 

 PI. Ind. Bulletin No. 175. 1910). 



