The Bitegmic Spermatophytic Ovule and the Cupule — A re-appraisal of the so-called Pseudo-monomerous Ovary

1. The ovules of all gymnospermous groups are essentially bitegmic. 2. The two integuments of the angiospermous ovule are the homologues of the two ovular coats of a gymnospermous prototype. 3. The cupule, a characteristic organ of pteridospermous and lower cycadopsid groups, is also represented by homologous structures in bennettitalean, chlamydospermous and angiospermous forms. 4. In the Higher Cycadopsida (including the Angiosperms) the homologue of the cupule is almost invariably one-ovuled, which is the result of a progressive oligomerisation of the number of ovules during its evolution from a primitive pluri-ovulate pteridospermous archetype. 5. Derivatives of the cupule in the Higher Cycadopsida include the interovular scales of cycadeoid groups, the chlamys of gnetalean forms and the true aril of the angiospermous ovule, but more important from a phylogenetic point of view is that in a number of angiospermous taxa the cupule homologue constitutes the outer wall (or at least a substantial part of the outer wall) of the ovuliferous gynoecial structure, i.e., of a pistil or ‘ovary’, or of an element of a phalangiate gynoecium. 6. The homology of some traditional angiospermous ‘pistils’ with a cupulate (chlamydote, arillate) ovule sheds light on the phylogenetic relationships between plants at a gymnospermous (chlamydospermous-bennettitalean) evolutionary level and a number of angiospermous forms, thus indicating that Angiosperms with carpellate gynoecia have attained a higher level of organisation and are derived from archetypes with primitive ecarpellate female genitalia. 7. From a discussion of the structure and vascularisation of the primitive angiospermous pistil of the cupulate ovule type the conclusion is drawn that the persuance of the interpretative floral morphology of one-ovuled pistils by means of anatomical studies is inadequate.