The small dorsiventral plants are in both cases floating aquatics.
A characteristic feature is the one-sided (dorsiventral) inflorescence, well illustrated in forget-me-not and other species of Myosotis; the cyme is at first closely coiled, becoming uncoiled as the flowers open.
Advance has been along two lines, markedly in relation to insect-pollination, one of which has culminated in the hypogynous epipetalous bicarpellate forms with dorsiventral often large and loosely arranged flowers such as occur in Scrophulariaceae, and the other in the epigynous bicarpellate small-flowered families of which the Compositae represent the most elaborate type.
In Monocotyledons a similar advance from hypogyny to epigyny is observed, and from the dorsiventral to the radial type of flower.
The flat branchlets of Cupressus, Thuja (arbor vitae), Thujopsis dolabrata (Japanese arbor vitae) are characteristic of certain types of conifers; in some cases the horizontal extension of the branches induces a dorsiventral structure.
Those of Ophioglossum are cylindrical, while the dorsiventral prothallus of Botrychium bears the sexual organs on the upper surface.
The prothallus developed from the spore is green and in most cases dorsiventral, bearing the archegonia and antheridia on the under surface.
The prothalli contain abundant chlorophyll, and are dorsiventral.