The leaves of very diverse species show a common method of leaf development in which the basipetal and basifugal directions of growth are combined. This is shown by the widespread occurrence of the ternate leaf with the three lobed apical leaflet and basally lobed proximal leaflets. This form appears with more or less distinctness in Clematis virginiana, Rhus toxicodendron, Rubus occidentalis, Rubus strigosus, Negundo aceroides, Ailanthus glandulosus, and Sium cicutaefolium. By the predominance of the basipetal or the basifugal element, palmate or pinnate leaves arc produced respectively. Twice pinnate leaves develop along the same plan; in becoming twice pinnate a basipetal secondary leaflet becomes matched by a smaller leaflet on the distal border and further development of secondary leaflets in basifugal. This is shown in Sambucus, Aralia, and Cicuta, and the exceptional nature of Bidens is recorded. The manner of leaf development in the rose requires further study. The formation of leaflets in connect...