146 



A TEXT-BOOK OF BOTANY. 



water and the mixture filtered, the filtrate does not give a reaction 

 with iodine solution ; if, on the other hand, the starch is previously 

 triturated with sand and then with water, the filtrate becomes blue 



Fig. 91. Larger grains of various starches as viewed through the micropolariscope 

 when mounted in oil: A, potato (70-80 m) ; B, wheat (30-40 m); C, ginger (30-50 m); D, 

 galangal (45-55 m); E, calumba (40-60 m); F, zedoary (50-75 1^); G. maranta (35-50 n); 

 H, colchicum (10-20 fi); I, com (20-25 f*); J. cassava (20-35^ ); K, orris root (30-35 m). 



on the addition of iodine solution. It appears that in the latter 

 operation the wall of the grain is broken and the soluble starch 

 present in the grain is liberated. 



