170 A TEXT-BOOK OF GRASSES 
are arranged ina 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,t 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, Egyptian corn, 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 sy a see O. Stapf, “Oil Grasses of India and 
Ceylon” (Kew Bull. Mise. Inf. 8: 1906). 
+See Ball, ‘‘History and Aidit Nie of Sorghum” (U. S. Dept. Agric. Bur. 
Pl. Ind. “Bulletin No. 175. 1910). 
