The Genesis of Form in Bulrush Millet (Pennisetum americanum (L.) K. Schum.).

Abstract

With the aid of three-dimensional, scale drawings the development of the shoot apex of bulrush millet is described from germination through its transition to the reproductive condition. The apex is remarkable in that the branch primordia of the inflorescence are arranged in regular spirals, and that this involves a transition from the distichous condition of the vegetative apex.

A number of phenomena relating to this transition support the view that physical constraint is a significant element in the determination of form, especially during early stages of development. Nevertheless, such constraint is seen mainly as a modifier of events at lower levels within the system. The new information is consistent with the mechanico-chemical field theory of phyllotaxis.