SPIROGYRA QUININA. 37 



ii. The number of turns of the spiral. 



iii. The surface, the crenulated and wrinkled 

 margin, and the turned up edges of the 

 band forming a more or less flattened Y m 

 optical section. To obtain a complete con- 

 ception of these particulars, first focus upon 

 the peripheral surface of the band, />., upon 

 the upper (outer) surface of the part nearest 

 the eye, then focus upon the axial (inner) 

 surface, and finally examine the profile of the 

 band seen on the right or left of the cell. 



iv. The nodules at varying distances along the 

 median line of the band. Stain with iodine 

 and note 

 a. An outer ring which is more deeply 



colored, starch, 4 and 



ft. A central light spot, pyrenoid. Both are 

 best seen when but faintly colored. 



v. The yellowish brown color finally imparted to 

 the chlorophyll band. 



b. The feeble brownish color given to the remainder 

 oT the contents of the cells, deeper along the 

 periphery. 



Run under glycerine on the same slide, and note 



c. The contraction of the colored protoplasmic part, 

 and its separation from the cell wall. 



d. In unstained cells presenting the least obstruction 

 from the chlorophyll bands, search for a colorless 

 irregular body with radiating arms, near the center 

 of the cell, the nucleus. This is difficult to demon- 

 strate in some species, but easily seen in others. 



4 Unless the plants have been in sunlight the preceding part of the day 

 the test for starch may not be fully successful. 



