From a developmental point of view, the flower can be regarded as a shoot axis of determinate growth, with the lateral members occupying the sites of leaves differentiating as floral organs sepals, petals, stamens, and pistils.
The wings of the dorsal (upper) sheath of the dithecous leaf point to the mother shoot axis of the branch.
Successive floriferous branches along the main stem disclose the shoot axis of A. riedelii as a monopodium (not sympodium) that develops an anthocladial (foliated) inflorescence in the form of a botrys or a compound botrys, respectively.
The dithecous leaf arises from the branch and not from the mother shoot axis – as previously believed – and represents the addorsed hypsophyll, i.e., the first leaf (prophyll) of the floriferous branch.
The single extant species of Ginkgophyta (Ginkgo biloba) has fleshy seeds produced at the ends of short branches on female trees, and Gnetum, a tropical and subtropical group of gymnosperms produce seeds at the tip of a shoot axis.
Our model also provides an insight into how shoot structures of plants has evolved between monopodial shoot axis and dichotomous shoot branching.
