16 STAKCHES. 



(11) Dioscorea Starch. 



This variety of starch (Fig. 11) is obtained from Dioscorea 

 alata, Linn., and other species of Dioscorea. It is often referred 

 to as British Guiana arrowroot, but is belter termed dioscorea 

 starch. The largest of the grains of which it is composed measure 

 45/i to 90/x in length and 25/x to 6(V in breadth, while the smaller 

 vary from 15/u. to 30/a in length and about half that in breadth. In 

 outline they are very variable, being often oval or elliptical, three- 

 sided, with rounded angles, or sometimes curved. The larger 

 extremity is often truncate and in the opposite narrower extremity 

 the hilum is situated ; this is rounded, eccentric and surrounded 

 by concentric striae. 



(12) Banana (or Plantain) Starch. 



This is obtained from the unripe fruits of Musa saoientuin, Liun., 

 and has ako been offered in commerce as Guiana arrowroot. 

 The grains are simple and show a great variation in outline ; some 

 are oval, ellipsoidal or elongated, whilst others are curved, bottle- 

 shaped, bean-shaped, etc. They are always flattened, and therefore 

 appear narrow and sausage -shaped when presenting their edges to 

 the observer. The hilum is rounded, situated near one extremity 

 and surrounded by concentric striae. The largest grains measure 

 45 to 65/i, the smallest about 7jw, intermediate grains from 22 to 

 3V 



The fruits from which the starch is prepared are often 

 distinguished as plantains, and the plant yielding them is some- 

 times distinguished by the name Musa paradisiaca, Linn. 





