Final answer:
Cytokinesis in the chlorophyceae involves a unique structure called a phycoplast, which is formed by microtubules perpendicular to the spindle.
Step-by-step explanation:
In the chlorophyceae, cytokinesis involves a unique structure called a phycoplast. The phycoplast is formed by microtubules that are perpendicular to the spindle during cell division. It helps to organize and guide the formation of the cell plate, which eventually leads to the formation of cell walls that separate the two daughter cells.