This investigation explores the relationship between increased energy levels and leaf morphology. It tests the idea that the causal agent of development is the dissipation of energy into transformed matter. The energy under which leaves developed was modified by increasing temperatures in grape cordons through wrapping them in clear plastic sleeves in the early spring. At the higher temperatures, and energy levels, there was a small but statistically significant decrease in leaf size and a change in organization the leaves. The decrease in leaf size may be due to a reallocation of resources, either to greater shoot growth as a previous study demonstrated or to the appearance of more vectors of development in the leaves, i.e. the appearance of more developmental subsystems. The leaves that grew under the higher temperature regime were more complex, perhaps indicating that the grapes on those same vines may produce more complex juice, another expression of more developmental subsystems. The change in organization in these leaves that developed at higher temperature argues that the causal agent in plant development is energy dissipation and the concomitant transformation of matter, the latter expressed in the appearance of more growth vectors.