THALLOPHYTES 



39 



and Spirogyra, the latter being especially abundant and long used for 

 laboratory study. They are both filamentous plants with elongated 

 cells, and differ from one another in the form of the conspicuous chloro- 

 plasts, which in Zygnema are two radiate or starlike bodies in each cell 



gf-^s^ 



106 -' 



Figs. 106— iro. — Spirogyra: 106, cell showing the spiral bandlike chloroplast con- 

 taining pyrenoids, and the centrally swung nucleus; 107, cells developing a conjugating 

 tube; 108, conjugating tube complete; 109, passage of one protoplast through the tube; 

 110, the zygospore. — After Coulter. 



(fig. Ill), and in Spirogyra, one or more bands that extend spirally 

 from one end of a cell to the other (fig. 106). Spirogyra may ht selected 

 to represent the family. The conspicuous green, spiral, bandlike 

 chloroplasts lie peripherally in the cell and contain conspicuous, nodule- 



