Algae exhibit the greatest variety of cell motility phenomena in the living world. These range from the peculiar gliding motility of filamentous blue- green algae or cyanobacteria to chloroplast movements and cytoplasmic streaming which are most common in higher plants. In addition, cell motility by eukaryotic flagella is the characteristic mode of cell locomotion in algal flagellates and most reproductive cells of algae. Algae use these cell motility systems mainly to orient themselves or their photosynthetic organelles in a suitable light gradient to optimize growth and reproduction. In...

Ralph A. LewiQand Lanna Cheng In physics, the discovery of new (more properly, hitherto undetected) particles has often resulted from a search: like the discovery of America, their existence had been postulated but their actual existence awaited confirmation. In biology, new discoveries are rarely made in this way. The existence of an alga like Prochloron, as a putative ancestor of chloro- plasts, had been postulated, but in fact its discovery was a consequence of fortuitous events. Green algal symbionts in didemnid ascidians had been known for decades to a few marine zoologists who had...