CLASSIFICATION OF ANGIOSPERMS. 



227 



the important cereals: Wheat (Triticum sativum and its varie- 

 ties), corn (Zea Mays), oat (Avena sativa), rice {Oryza sativa), 

 barley {Hordeum sativum and its varieties), rye {Secale cereale). 

 A number of the species yield a sweet cell-sap from which cane 

 sugar is made, of which the most important are the sugar cane 

 (Saccharum oMcinarum) and sorghum (Andropogon arundina- 

 ceus saccharatus and other varieties). 



Fig. 125. Wheat (Triticum): A, zigzag axis or rachis of ear showing the notches 

 where the spikelets were inserted; B, an entire spikelet; C, a flower with the pales; D, a 

 flower without the pales, showing the lodicules at the base; E, glume; F, outer pale; G. 

 inner pale; H, fruit (caryopsis) ; I, longitudinal section of fruit. — After Warming. 



A large number of the grasses are used in medicine, one of 

 which, couch-grass {Agropyron repens), is official (p. 490). 



Agropyron repens is a common perennial grass, forming slen- 

 der jointed rhizomes, by means of which the plant is extensively 

 propagated; the culms vary from one to four feet in height, the 

 spikelets are 3- to 7-flowered; and the empty glumes, 5- to 

 7-nerved, acute or with an awn-like apex (Fig. 214). 



