The measured divergence angles between successive primordia in the developing flower were compared with angles expected on several hypotheses concerning primordial initiation. The results lead to the conclusion that the position and sequence of initiation of the younger sepals is determined by the older ones but that the influence of an older primordium lasts for only two plastochrons. The petals and carpels are apparently positioned by the sepals. The positions of the stamens are consistent with their king determined by the sepals (antesepalous stamens) or petals (antepctalous stamens), but their sequence of initiation is consistent with its being determined, like the sepals, by the two youngest primordia. The data indicate that there are two sets of factors governing the initiation of the primordia subsequent to the sepals: one governing the positioning of the primordia and resembling the factors governing the positions of axillary buds, and the other governing the sequence of primordia and resembling the factors which determine the initiation of leaves. Measurements of the plastochron ratios were used to calculate the sizes of the sepal, petal and stamen primordia at initiation. At the moment of initiation the sepal primordia were about one third, and the petal and stamen primordia about one sixth, of the size of the leaf primordia. In its early development the Silene flower therefore resembles a condensed leafy shoot with precocious axillary buds but with primordia which are small compared to leaf primordia.