THE STARCH CELL. 



37 



trated sulphuric acid, or oil of vitriol. Our readers, whilst repeating this experiment, 

 must exercise the greatest caution lest they burn their fingers and clothes. The fol- 

 lowing is Mr. Busk's method : "A small quantity of the starch is placed upon a slip 

 of glass, and covered with five or six drops of water, in which it is well stirred about ; 

 and with the point of a slender rod of glass the smallest quantity of solution of iodine 

 is applied, which is to be quickly and well mixed with the starch and water. Any 

 excess of water must be allowed to drain off, leaving the moistened starch between, 

 and a portion of it 

 is then to be covered 

 with a piece of thin 

 glass. It must then 

 be placed on the 

 microscope, and a 

 quarter or one-fifth 

 object glass brought 

 to a focus close to 

 the upper edge of 

 the piece of thin 

 glass. With a slen- 

 der glass rod a small 

 drop of sulphuric 

 acid is to be care- 

 fully placed imme- 

 diately upon, or 

 rather above, the 

 edge of the cover, 

 care being taken 

 that it does not run 

 over it. The acid, 

 of course, quickly 

 insinuates itself be- 

 tween the glasses, 

 and its course may 

 be traced by the 

 rapid change in the 

 appearance of the 

 starch grains with 

 which it comes in 

 contact. The course 

 of the acid is to be 

 followed by moving 

 the object up wards ; 

 and when, from its 

 diffusion, the re- 

 agent begins to act 

 more slowly, the 



peculiar changes in the starch granules, now also less rapid, may be readily witnessed." 

 M. Martin thus describes the changes observed by him : " First the starch grain 



Fig. 79. 



