The common "monkey ladder" of tropical forest is the sculptured main stem of a Bauhinia liana. This photograph was taken by Dr. Mildred Mathias in 1961 in the Peruvian Amazon. The common "monkey ladder" of tropical forest is the sculptured main stem of a Bauhinia liana. This photograph was taken by Dr. Mildred Mathias in 1961 in the Peruvian Amazon.