Studies on seeds with ruminate endosperm - III. Development of rumination in certain members of the apocynaceae
The unitegmic, tenuinucellate ovules ofVoacanga grandifolia andErvatamia heyneana of the Apocynaceae show massive-chalazal growth after fertilization. The integumentary part of the ovule also grows to a certain extent. Due to differential growth activity of the inner layers and the epidermis, the latter forms infoldings into the former. The epidermal layer becomes thickened in a peculiar manner, but the inner layers remain thin-walled. The endosperm develops late and becomes ruminate by replacing all the inner layers of thin-walled cells and leaving intact the epidermis alone with its infoldings as the mature seed coat. Outgrowth from around the funicle forms a prominent aril inErvatamia heyneana and a common fleshy mass around the seeds inVoacanga grandifolia.
InTabernaemontana sp. chalazal growth is lesser, and even though the seed surface becomes irregular during early stages, the endosperm does not become ruminate.