FIG. 27.15 Diversity of green algae. (a) Chlamydomonas reinhardtii, a tiny flagellated unicell widely used in laboratory research on photosynthesis; (b) Spirogyra, a freshwater green alga with distinctive helical chloroplasts; (c) a desmid, among the most diverse and widespread of all green algae in fresh water; (d) Volvox, a simple multicellular organism; and (e) Acetabularia, a macroscopic (but single-