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 
106 - 
FIGS. 106-110. Spirogyra: 1 06, 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; 
no, the zygospore. After COULTER. 
(fig. in), and in Spirogyra, one or more bands that extend spirally 
from one end of a cell to the other (fig. 106). Spirogyra may be selected 
to represent the family. The conspicuous green, spiral, bandlike 
chloroplasts lie peripherally in the cell and contain conspicuous, nodule- 
