Organisms popularly called “algae” include such diverse groups as the giant seaweeds and the microscopic desmids. In fact, the classification and evolution of the various algae on Earth—past and present—is a matter of intense scrutiny and discussion among scientists today. The Garden’s research focuses primarily on “green algae,” organisms closely related to the first plants that invaded land some half a billion years ago. The nearly 14,000 species of green algae found worldwide are important primary producers, playing essential roles in many ecosystems from extremely dry deserts to coral reefs. Green algae also provide food and shelter for a variety of other organisms.