468 



A TEXT-BOOK OF BOTANY. 



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

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



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 a.n awn-like apex. 



Hordeum sativum is an annual grass with the flowers in ter- 



F!G. 255. 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. 



minal cylindrical spikes resembling wheat. The spikelets are ses- 

 sile, i-flowered, and usually in clusters of three on opposite sides 

 of the notched rachis. The empty glumes are long and narrow, 

 forming a kind of involucre around the spikelet. It is supposed 

 that Hordeum sativum is a cultivated form of H. spontaneum 

 growing in the countries between Asia Minor and other parts of 

 Western and Southwestern Asia. Three important varieties are 

 distinguished, depending upon the number of rows of grains in 



