HISTOLOGICAL STUDIES 37 



ing, the best results are obtained if nearly all the light is 

 excluded by the diaphragm. 



Draw what you see. Note that the masses are made up 

 of separate elements (cells). Compare with Fig. 12, A. 

 Are the walls circular as in the figure? 



Place a drop of the methyl green at one side of the cover 

 slip and by placing the filter paper at the opposite side draw 

 this solution under the slip. Let the slide stand for a mo- 

 ment and examine again with the low power. What part 

 of the cell has changed color? (This part is called the nu- 

 cleus of the cell.) 



Now focus on one of these cells with the one-sixth ob- 

 jective (high power). Has the cell a definite outline? Note 

 the clear liquid between the nucleus and the outline. Do 

 you notice any particles floating in this liquid? Draw this 

 cell, magnified to an inch diameter, and label as follows : the 

 outside boundary, or cell wall] the clear liquid, or protoplasm; 

 the particles floating in this protoplasm, or granules; the 

 nucleus. 



XXIII. STUDY OF A PLANT CELL. 



Apparatus. Pond scum (Spirogyra), normal salt solution, 1 ma- 

 terials described in Ex. XXII. 



Directions. Mount a little of the pond scum in a drop 

 of water and cover with a glass. Examine with the low 

 power. Do you see any separate units in this case? How 

 are they arranged? What is their color? Is this color 

 evenly distributed throughout the cell or located in definite 

 parts of the cell? Can you see any cell wall? protoplasm? 



1 Normal salt solution is made by adding six-tenths of one per cent of 

 common salt (NaCl) to distilled water. 



