Amongst gamopetalous plants several of our largest living families, including Campanulaceae, Labiatae, Solanaceae and Primulaceae, are still missing; and of Boragineae, Scrophularineae, Gentianeae and Caprifoliaceae there are only faint and doubtful indications.
So also in Labiatae, such as dead-nettle (Lamium), the different whorls of inflorescence are developed centripetally, while the florets of the verticillaster are centrifugal.
This mixed character presents difficulties in such cases as Labiatae, where the leaves, in place of retaining their ordinary form, become bracts, and thus might lead to the supposition of the whole series of flowers being one inflorescence.
When a flower can be divided by a single plane into two exactly similar parts, then it is said to be zygomorphic. Such flowers as Papilionaceae, Labiatae, are examples.
52); or along with the corolla, as in Ranunculus, and is deciduous; or it remains after flowering (persistent) as in Labiatae, Scrophulariaceae, and Boraginaceae; or its base only is persistent, as in Datura Stramonium.