A computerized analysis of the occurrence among 291 dicotyledon families of 107 morphological or biochemical characters is described. The results confirm earlier work and increase the number of characters that are shown to be statistically associated from 26 to 39. Many of these occur more often in rain-forest floras than in the rest of the world. They also occur more often in families that are represented in the fossil record than they do in the present-day world flora, and are therefore regarded as primitive.

Using 30 of these correlated characters, the percentage advancement index of the various families is calculated. Among the most advanced families are Dipsacaceae, Valerianaceae and Hippuridaceae. The most primitive ones are Aextoxicaceae and Degeneriaceae, with Stachyu-raceae and Magnoliaceae also very primitive.