SPIROGYRA. 41 



(5) The yellowish-brown color finally imparted to the 

 chlorophyll band. 



b. The feeble brownish color given to the remainder of the 

 contents of the cells, deeper along the periphery. 



c. In cells presenting the least obstruction from the chloro- 

 phyll bands search for a colorless oval or spindle- 

 shaped body, the nucleus, 1 imbedded near the center of 

 the cell in a mass of protoplasm with arms radiating to 

 the peripheral protoplasm. The peculiar conditions 

 found here would at first glance lead one to suppose 

 the real nucleus to be a nucleolus. 



II. REPRODUCTIVE CHARACTERS. 



Mount fi'aments thought to be in reproductive stage, and 

 under low power search for: 



1. Filaments lying side by side in pairs, held together by 

 transverse branches, the conjugating tubes. 



2. Some filaments having an irregular outline, caused by 

 uneven lateral expansions, the beginning of conjugating 

 tubes. When conjugating filaments are found, observe: 



3. The varying character of the contents of the cells: some 

 with spiral bands of chlorophyll; some with a confused 

 green mass; some with green or brown oval bodies, the 

 zygospores; some empty. 



Under high power observe : 



4. The conjugating tube connecting two cells: 



a. The enlargement at the middle, where an indentation 

 marks the line of union of the two originally separate 

 branches. 



6. What variations in directions of the conjugating tubes 

 can be found ? 



1 This is not easily demonstrated in all species, although the iodin 

 usually stains it a light brownish color. 



