SPIROGYRA QUIN1NA. 39 



a. By studying various specimens, trace the changes 

 from the vegetative condition, through the several 

 stages of disintegration of the chlorophyll band 

 and contraction of the protoplasm to the forma- 

 tion of a rounded uniformly greenish-brown mass ; 

 noticing at the same time, that this change takes 

 place side by side with the formation of the conju- 

 gating tube. In general all the stages are easily 

 found. 



b. Where the conjugating tube is fully formed, note 

 that one cell is empty, and the connected cell con- 

 tains a single mass, the spore produced by the 

 conjugation. 



7. The mature zygosporc : note 



a. The shape and color. 



b. The contents. 



c. The wall of greater or less thickness, usually 

 resolvable into two or more layers of different 

 colors. 



8. Make drawings to illustrate the parts and changes of 

 the fruiting filaments. 



ANNOTATIONS. 



In the form and manner of growth of Spirogyra, we 

 meet with no features not seen in Oscillaria or Proto- 

 coccus, except the arrangement of the protoplasm and 

 chlorophyll bodies. The filaments are built on the 

 plan of Oscillaria, with the cells larger, and the sheath 

 so much reduced that it can be demonstrated only with 

 difficulty. In some species of the closely related genus 

 Zygnema, however, the sheath is readily discernible. 

 The increase in the number of cells is effected in the 



