In spite of the part played by the Yam tuber in the clone perennity and economical value, its anatomy remains insufficiently studied. A simple study of D, alata, D. trifida, D. cayenensis, D. escu/enta and D. transversa sets up characters which enlighten tue species biology. In D. alata a very specific sclerenchymatous zone is interpreted as transfusion tissue. In all the species, cellular blocks, within the inner cortical parenchyma, make up the organizing poles of the tuber part set germination.