I40 BOTANY OF CROP PLANTS 



Mature Grain of Barley. — In hulled barleys, the palet and 

 lemma are firmly attached to the kernel (Fig. 51). In the 

 so-called "naked" or hull-less barley, these scales come loose 

 from the kernel, as in common wheat. The kernel of naked 

 barley resembles that of wheat. It is, however, pointed at 

 both ends (Fig. 51). The kernels are broadest at the 

 middle, in two-rowed barleys, while in the four-rowed types 

 the kernels from the outer rows of the head are slightly 

 twisted and those from the middle rows are broadest near 

 the tip. 



In the hulled barleys, a rachilla ("basal bristle") persists 

 at the base of the grain on the side adjacent to the palet 

 (Fig. 51). The character of this bristle is of some syste- 

 matic importance. 



The hull may form from 10 to 25 per cent, of the grain, 

 being greater in six-rowed types than in two-rowed types. 

 Variation in percentage of glumes may depend upon season, 

 soil, grain shape, and perhaps fertilizers. Furthermore, 

 Haberlandt has shown that barleys of northern regions have 

 a smaller percentage of hull than those of southern localities. 



In a cross-section of the mature grain of hulled barley, the 

 following coats are seen: 



1. Lemma and palet, five to seven rows of cells. 



2. Pericarp, consisting of several rows of parenchyma cells 

 and two rows of chlorophyll-bearing cells. 



3. Testa, two layers of inner integument. 



4. Nucellus, one row of cells. 



5. Aleurone layer, usually of three (two to four) rows of 

 thick-walled cells. 



6. Starchy endosperm. 



As in rye and wheat, the fruit and seed coats are more 

 weakly developed at the embryo end than in other parts of 

 the igrain. 



