(WITH FIVE FIGURES) Although the physiology of tendrils has been exhaustively studied, comparatively little work of an anatomical nature has been done. In reviewing the literature included in this paper, all references are to the structure of tendrils in general, unless specific examples are given. PENHALLOW (6), in investigating the movements of Cucurbita maxima and C. Pepo tendrils, considered at some length their histological structure. In cross-sections of squash tendrils he found beneath the epidermis a somewhat thick layer of collenchyma, its continuity broken at three points by parenchyma tissue. The three parenchyma regions were found upon the upper side and the right and left. The cells of these regions were large, rounded, and somewhat thin-walled. They contained protoplasm and considerable chlorophyll. Within these areas were intercellular spaces with corresponding stomata in the epidermis. PENHALLOW found that in these parenchyma regions the greatest growth occurred without regular order, but in turn. He gave to this tissue the name vibrogen, signifying that the region of circumnutation was to be found there. Within the layer of collenchyma were found three or four rows of rather large and rounded parenchyma cells. These cells were filled with "protoplasm, chlorophyll, and other granular matter." The amount of chlorophyll was much less than in the vibrogen region with which this tissue was connected. Beneath the parenchyma were found wood cells. In the early period of growth of the tendril, the wood tissue formed a crescent along the lower side. Later, breaks were found in the tissue corresponding to the position of the vibrogen regions. Finally these breaks were found to close up, and the tissue became a ring of wood. With age the wood cells developed thick walls. Next in the remaining tissue were found the fibrovascular bundles, seven in number. The central pith