402 STARCHES, GLANDS, &c. 



38 microns l (/x) in diameter, the smaller of the large grains 15 to 25, 

 whilst the small grains average 6 to 7. 



Maize Starch consists of grains that are nearly uniform in size and 

 rather smaller than the large grains of wheat starch ; (mostly 12yit to 

 ISyLt ; they are polygonal with blunt angles, or more or less rounded. 

 In the centre there is often a small cleft, or two or three radiating from 

 a centre (the hilum). 



Rice Starch consists of extremely minute grains, averaging about 

 6/j, in diameter. They are polygonal, with sharp angles, and without 

 evident concentric striae, hilum, or cleft. 



Varieties. The following varieties of starch, although not official 

 are sufficiently important to call for remark : 



Potato Starch, obtained from the tubers of Solanum tuberosum, 

 Linne (N.O. Solanacece), is extensively employed for various technical 



FIG. 221. Rice Starch. Magnified 300 

 diam. (Tschirch.) 



purposes and has been frequently used to adulterate maranta starch 

 and certain drugs. 



The grains are much larger than those of any of the official starches, 

 varying mostly from 45/i, to 75yLt in length and from 45/i, to 60/z in 

 breadth ; larger grains may occasionally be found and smaller ones 

 are by no means uncommon. They have usually a flattened ovoid 

 shape and possess a small hilum that is often situated near the 

 narrow extremity of the grain, whilst the broad end frequently 

 exhibits a sinuate outline ; the concentric strise are well marked. 



Maranta Starch, obtained from the rhizomes of Maranta 

 arundindcea, Linne (N.O. Marantacece), is known in commerce as 

 St. Vincent, Bermuda, and Natal arrowroot, or simply as arrowroot, 

 but as the latter term is applied to a number of other starches, it is 

 desirable that this, the arrowroot of English commerce, should be 

 specified as maranta starch. Thus the starch of Curcuma angusti folia, 

 Roxburgh, and C. leucorhiza, Roxburgh (N.O. Scitaminece), is known 



1 A micron is the one-thousandth part of a millimetre. 



