10 STARCHES. 



(5) Oat Starch. 



Oat starch (Fig. 5) is contained in the fruits of Avena sativa, 

 Linn. It consists of two kinds of grains, viz., simple and com- 

 pound. 



The simple grains average about W/j, in diameter. They are 

 mostly rounded in outline ; very few are angular, but some are 

 spindle-shaped or lemon-shaped. The latter should be specially 

 noted as they form a distinctive feature of oat starch. 



The compound grains are oval or rounded and more or less 

 regular in shape, ranging usually from 35^, to 45/t in length, but 

 attaining as much as 50/u. They consist of a varying number (5 to 

 200) of grains compacted together. The constituent grains vary in 

 shape according to the position they have occupied in the compound 

 grain. Those from the centre are angular, whilst those from the 

 periphery are curved on one side and angular on the other ; they 

 are generally rather smaller than the simple grains. 



(6) Rice Starch. 



Rice starch (Fig. 6) is obtained from the fruits of Oryza sativa. 

 Linn. Like oat starch, it consists of both simple and compound 

 grains. 



The simple grains are tolerably uniform in size and shape ; they 

 range from 4/x, to 6/t, sometimes reaching B/J,, and are generally 

 angular. 



The compound grains are ovoid or rounded in shape, but vary 

 very much in size, according to the number of constituent grains 

 that they contain. 



Rice starch closely resembles oat starch ; the grains are, how- 

 ever, uniformly rather smaller and never spindle- or lemon-shaped, 

 When treated with water the compound grains are readily disso- 

 ciated into their constituent grains, and so it happens that the 

 former arc seldom found in the rice starch of commerce. 



