These are the elaborately entwined vines of the old “Tarzan” movies. Although they begin life on the ground and their woody stems remain rooted to the forest floor, tendrils attach to neighboring trees, and, entwined around their host, these hitchhikers climb to the canopy on the backs of other trees. Up in the treetops, lianas spread and a single vine can loop its way through a number of trees. Lianas are springy and strong, able to support an adult’s weight. Some have hollow stems that contain water that can be gotten with the aid of a machete. Lianas can weigh down a tree so much that wind and weather collapses it more easily. A fallen liana just moves and grows on another tree.