34: 



THE SAGO PALM. 



cally demonstrated, if a drop of a solution of iodine be added to the smallest quantity 

 of starch and water, and placed under the microscope. The chemical effect of the 

 iodine is to colour the starch of a beautiful deep violet shade. We may also add, that 

 as starch has the property of polarizing light, its presence may be readily shown by 

 placing it in the microscope with the polarizing apparatus. 



Fig. 77. The SAGO PALM (Cycas revoluta), contain 1 ! g a large quantity of starch in its stem. 



Further attention is, however, necessary to the consideration of the second kind of 

 starch, or that consisting of cells ; and chiefly on the ground, that it is possible to dis- 

 tinguish the starch grains or cells of one plant from those of another, and thus to 

 detect the adulterations which are practised in reference to flour, bread, arrow-root, 

 and other articles of farinaceous food. Much attention has been given to this mattei 

 during the past ten years, and with the result, it is believed, of having lessened, at Least, 

 the frequency with which fraud has been perpetrated. 



Starch grains are distinguished from each other by their size, figure, and markings. 



