The existing investigation of Stephen Hales's Vegetable Staticks have focused on the chapter six of the text, since they emphasized Hales's discovery of "fixed air" and the importance of Hales's matter theory in the development of 18th-century matter theory. Therefore Hales's study of the physiological phenomena of vegetables, which was the main interest of Hales, has been treated superficially and there have been few attempts to obtain structural undertanding on Vegetable Staticks. This paper investigates the way that Hales approached the physiological phenomena of vegetables, following the chapters of Vegetable Staticks in order. In chapter II, III, and IV of this paper, the motion of sap and the production and growth of vegetables, which Hales dealt with seriously, are discussed. From these discussions, it is revealed that Hales explained the physiological phenomena with the mechanism which employed the Newtonian forces, namely, attraction and repulsion. Sometimes, Hales would explained the physiological phenomena with the concept of the harmony of Nature. As Nature is harmonious, Nature supplies the plant with the proper quantity of nutriment in proper time and the plant forms its new parts, namely, branches, leaves, and blossom in proper time. But this attitude does not mean that Hales rejected the mechanical approach to the physiological phenomena. Since he explained the general situation of physiological phenomena with the mechanism, he had an idea that the concept of harmony of Nature could be explained with the mechanical approach. Hales was a sincere Newtonian, trying to explain physiological phenomena with the mechanism which employed the Newtonian forces.