STARCH. 



57 



Fig. 3. 



STARCH GRAIUS OF BERMUDA ARROW- 

 ROOT. 



after extraction of the granulose, though it may be reduced to five or 

 six per cent, of its original weight. 



The starch grains of the potato (Fig. 2) vary considerabl} 7 in size. 

 The smallest have a diameter of 2.5 inmm., 1 the largest 62.5 mmm. 

 They are irregularly pear-shaped 

 in form, and their concentric 

 markings are very distinct. The 

 starch obtained from the potato, 

 however carefully prepared, re- 

 tains in connection with it traces 

 of an odoriferous principle which 

 makes it less valuable for culi- 

 nary purposes than many other 

 varieties. 



The starch granules of arrow- 

 root (Fig. 3) are generally 

 smaller and more uniform in 

 size, than those of the potato. 

 They vary from 12.5 mmm. to 

 50 mmm. in diameter. They are 

 elongated and cylindrical in 

 form, and the concentric mark- 

 ings are less distinct than in the preceding variety. The hilum has here 

 sometimes the form of a circular pore, and sometimes that of a trans- 

 verse fissure or slit. 



The grains of wheat starch 

 (Fig. 4) are still smaller than 

 those of arrowroot. They vary 

 from 2.5 mmm. to 35 mmm. 

 in diameter. They are nearly 

 circular in form, with a round 

 or transverse hilum, but with- 

 out any distinct appearance of 

 lamination. Many of them are 

 flattened or compressed later- 

 ally, so that they present a 

 broad surface in one position, 

 and a narrow edge when viewed 

 in the opposite direction. 



The starch grains of Indian 

 corn (Fig. 5) are of nearly the 

 same size with those of wheat 

 flour. They are somewhat more irregular and angular in shape ; and 



1 The sign mmm. stands for micro-millimetre ; that is, the one-thousandth part 

 of a millimetre. A millimetre is very nearly equivalent to one twenty-fifth of an 



Fig. 4. 



STARCH GRAINS OP WHEAT FLOTTR. 



inch ; and a micro-millimetre, accordingly, is about 

 5 



of an inch. 



