10 STUDIES IN HISTOLOGY. 



V. PiiOTEiN Granules (pages 44-47 and 182). 



Examine thin sections of the endosperm of the seed of Ricinus 

 after the specimen has been treated as directed in 176, and also 

 of the seed of BevthoUetia (Brazil-nut) . Permanent preparations 

 from the latter should be made as directed on page 47. 



Search also for cubical crystalloids in the cells just under the 

 skin of a potato-tuber. 



VI. Starch. 



In the examination of starch (pages 47 and 181) make thin 

 sections of (a) a potato-tube)', (b) the cereal grains figured in the 

 pages cited, (c) seeds of the pea and bean. 



Detach some medium-sized starch-granules and measure them 

 with the micrometer ; after this applj' a solution of iodine, em- 

 plo\-ing the most dilute one which will impart a decided color to 

 the granules. Is the color given b}' iodine permanent? Does 

 exposure of the colored specimen to light make anj- difference in 

 permanence of color ? 



In all cases note very carefully- any appearance of stratifica- 

 tion which the different granules present, and determine the 

 distinctive characters by which each of the common commercial 

 starches can be recognized, such as rice-starch (toilet-powder), 

 laundrj- starch (either wheat or potato), etc. After sufficient 

 familiarity has been acquired b3' an examination of all the 

 kinds of starch figured in Part I., try to identif}' nnder the 

 microscope specimens of laundry starch and of various kinds 

 of flour. 



Can starch be detected in the following : — ■ 



Seeds of flax and mustard? 



Roots of beets and turnips? 



Pulp of the ripe and the unripe apple? 



Bark of willow and maple ? 



Young shoots of pine ? 



For the detection of starch in minute amount in chlorophyll 

 granules the directions given on page 42 must be carefully 

 followed. 



From this time on, the character of the granules seen in any 

 specimen should be determined by iodine and the result noted 

 in the drawing. 



