STARCHES. 



(3) Barley Starch. 



Barley starch (Fig. 3) may be obtained from the fruits of 

 Hordeum distichon, Linn., and other species of Hordeum. 



Like both the preceding starches, barley starch also consists of a 

 mixture of large and small grains, with few of intermediate size. 

 They are rather smaller than the grains of wheat starch, and are 

 also distinguished by their outline, which is less regular and often 

 bears protuberances. In surface view the large grains are seldom 

 round ; they are more often slightly elongated or elliptical, some- 

 times reniform, bulb- or pear-shaped. In diameter they vary from 

 20/j, to 35/x, many being between 20//. and 25//,. They have no 

 apparent hilum, but some of them exhibit concentric striations. 

 They are seldom fissured at the hilum, and when that is the case 

 the fissure is much less conspicuous than it is in rye starch, and 

 never stellate. 



The grains of medium size vary from 10/t to 15/x, in diameter, 

 the small ones are about the same as those of wheat or rye-starch. 



(4) Maize Starch. 



Maize starch (Fig. 4) is obtained from the fruits of the Zea 

 Mays, Linn. The grains of maize starch exhibit a certain 

 difference in shape according as they are derived from the mealy 

 centre of the endosperm or from the translucent horny periphery. 



Those from the centre of the grain, having been subjected in a 

 less degree to mutual pressure, are irregularly rounded in shape, or 

 at least not markedly angular ; some are nearly round, others are 

 elongated, oval or pear-shaped. The hilum is always rather large 

 and conspicuous ; the grains measure from 10/i to 25//, in diameter, 

 the average being about 13/x to 15/t. 



The grains from the horny part of the endosperm exhibit an 

 angular contour due to the mutual pressure to which they have 

 been subjected. Their appearance under the microscope varies 

 considerably according to the position in which they lie. They 

 are always easily recognised by their regular shape, angular out- 

 line, more or less uniform size, and, by the presence of a distinct 

 hilum, which is sometimes rounded, but more often fissured, or 

 stellate. The diameter of these grains averages from 14^ to 15/x, 

 but may sometimes reach 25/x or 26^,. 



