"In Fig. 16, although the leaf patterns are varied, their emotional impacts are perceived to be about the same. Why? Because all structural lines are parallel, promoting direction and flow.

Again in Fig. 17 similar line structures yield completely different impact emotionally. Why? The answer lies in the line relationships, or relativity. In Fig. 17-B the leaves are somewhat grotesque since not all of the parts are in harmony.

In Fig. 18-A there are seven lines, properly placed, making up a pleasing leaf structure. The whole is graceful, flowing, and in harmony with each of its individual parts. Look closely and you will see that all of its parts are flowing in the same direction with only slight deviations from this rule.

Fig. 18-B shows examples of leaf structures similar to those in 18-A. Each of these structures is different from the others, but the visual motion of the leaves is maintained by the parallel lines. "