MICROSCOPIC OBJECTS. 85 



Fossil Char a Seeds are interesting opaque objects. 

 They are globular, and the surface is grooved, with 

 spirals running from one pole to the other. A group of 

 four or five seeds on a black disc, with a power of 30 

 diameters, affords much instruction. 



Starch. — The ordinary starch of the laundress, which 

 is an impure substance combined with a blue earthy pig- 

 ment, is not the material to be here described as a mi- 

 croscopic object. The pure vegetable proximate principle 

 called by chemists starch, of which arrowroot is a com- 

 mon sample, is the subject of the following remarks. 



The granules of starch obtained from different plants 

 are found, when examined under the microscope, to differ 

 in size and form. Some are spherical, others elliptical, 

 flask-shaped, polyhedral, &c. Hence this method of 

 examination affords a ready means of detecting fraud in 

 the substitution of one kind of grain for another. The 

 starch granules, although so very minute, are composed 

 of a fine and delicate membrane inclosing a fine mealy 

 powder. It may not be unaptly compared in some par- 

 ticulars to a common pea, in which the legumen is in- 

 closed in a testa or skin. Of course the comparison will 

 not hold as regards the functions of the two. Starch 

 granules are not soluble in cold water, nor is iodine 

 capable of acting upon them while the membrane in- 

 closing its contents remains whole. Indeed it is a most 

 remarkable fact, that a membrane so delicate and thin 

 that it is immeasurable by the most accurate micrometer, 

 should resist so powerful a substance as iodine. If the 



