144 BOTANY OF CROP PLANTS 



istic of barley. The term ^^ aero spire'' is sometimes applied 

 to these leaves. 



The crown roots are formed at a rather constant soil level. 

 If the grain is planted deep, a long internode is formed, such 

 that adventitious roots are produced at the proper level. 



Classification of Barleys. — There is much difference of 

 opinion concerning the classification of the cultivated barleys. 

 There are at least two distinct species: Hordeum vulgare, in- 

 cluding the six-rowed barleys, and Hordeum distichon, 

 including the two-rowed barleys. 



Hordeum vulgare hexastichon (six-rowed barley). — It will 

 be recalled that, in the barleys, there are three one-flowered 

 spikelets at each joint of the rachis. In the six-rowed type, 

 every flower of a triplet is fertile. The spikelets are in six 

 distinct rows and stand out equidistant from the rachis. 

 Furthermore, the rows are equal distances from each other 

 about the axis. These points are shown in Fig. 52. The 

 lemmas of all three spikelets are bearded. The rachis inter- 

 nodes are very short, from 2.1 to 2.7 millimeters long. The 

 kernels from the outer rows are twisted, those from the 

 middle row broadest near the tip, and symmetrical. The 

 "hull" is thick. These are both winter and spring sorts. 

 Six-rowed types are food barleys. 



Hordeum vulgare (common six-rowed barley). — This is 

 sometimes called a four-rowed barley. Every spikelet is 

 fertile; the lemmas of all spikelets are bearded or hooded; 

 the "hull" is thick; and there is a high percentage of protein. 

 It differs from six-rowed barley in that the rows of grains are 

 not equal distances from each other about the axis (Fig. 

 52). The lateral grains of one triplet tend to overlap with 

 the lateral grains of the triplet on the opposite side of the 

 rachis. Hence, there will be found often four rows of grains, 

 the central grains of each triplet forming two rows and the 



