Alec Holland!

Swamp Thing is an elemental creature who shares a connection to all plant life on the planet Earth through a network called the Green. He is a mass of vegetable matter that absorbed the memories and personality of Alec Holland, a botanist who died in a swamp shortly after creating a hormonal Bio-Restorative Formula for plants. He is associated with the Parliament of Trees, the White Lantern Corps, and the Justice League Dark.Swamp Thing was created by Len Wein and Bernie Wrightson, first appearing in House of Secrets#92. (1971)