Precise numbers are difficult to determine, but as of 2010, there are thought to be 300–315 thousand species of plants, of which the great majority, some 260–290 thousand, are seed plants (see the table below). Green plants provide most of the world's molecular oxygen and are the basis of most of the earth's ecologies, especially on land. Plants that produce grains, fruits and vegetables form mankind's basic foodstuffs, and have been domesticated for millennia. Plants are used as ornaments and, until recently and in great variety, they have served as the source of most medicines and drugs. The scientific study of plants is known as botany, a branch of biology.
Trigun revolves around a man known as "Vash the Stampede" and two Bernardelli Insurance Society employees, Meryl Stryfe and Milly Thompson, who follow him around in order to minimize the damages inevitably caused by his appearance. Most of the damage attributed to Vash is actually caused by bounty hunters in pursuit of the sixty billion double dollar bounty on Vash's head for the destruction of the city of July. However, he cannot remember the incident due to retrograde amnesia, being able to recall only fragments of the destroyed city and memories of his childhood. Throughout his travels, Vash tries to save lives using non-lethal force. He is occasionally joined by a priest, Nicholas D. Wolfwood, who, like Vash, is a superb gunfighter with a mysterious past. As the series progresses, more about Vash's past and the history of human civilization on the planet Gunsmoke is revealed.