Gentianaceae - Gentian Family

Common Centaury (Centaurium erythraea)

The Gentians typically have pentamerous flowers (flowers with 5-rayed symmetry, i.e 5 sepals, 5 petals and 5 anthers): floral formula = * K5 [C(5) A5] G(2) with the petals fused into a corolla tube, with the 5 petals alternating with the 5 stamens which are also fused to the corolla by their filaments. However, 4 rays or 6 to 12 rays of symmetry occur in some species. The Common Centaury (Centaurium erthraea) pictured above and below is a plant of dunes and dry grasslands, pictured here growing on chalk grassland.

Yellow-wort (Blackstonia perfoliata)

The leaves of Blackstonia are 6 to 8-merous and the leaf bases fuse completely around the stem (the leaves are connate) such that the stem appears to pierce the leaves (hence 'perfoliata'). The 6 to 8 petals are fused into a corolla-tube and the flowers close in early afternoon. This plant is found on chalk grasslands and so may co-exist with Common Centaury, but the two plants seem to prefer different microhabitats.

Autumn Gentian (Gentianella amarella)

The flowers of Autumn Gentian are 4 or 5-merous and the four or five petals are again fused into a corolla with a fringe of pale hairs or filaments in the throat. This plant is found in northern temperate and arctic regions. Here it is growing on calcareous grassland.

This plant was said to have been used by the Centaur Chiron to cure himself of a wound inflicted by Hydra. It has long been used in traditional medicine. Science has shown that the plant is rich in polyphenolics (phenolic acids and xanthones) which are efficient antioxidants.

As can be seen in these images, the anthers coil upon dehiscence. The seeds are minute and have a reticulate (net-like) surface sculpturing. There are about 30 species of Centaurium, distributed across North America, Europe and Africa.

Gentians in general will close their flowers at night and in dull weather. The throat of the corolla tube is whitish and lighter in hue than the petal lobes, as in many trumpet-shaped flowers. A < pollinating insect entering the corolla will find itself in a bright surround. The nectaries are borne on the inside of the corolla tube at its base.

The flowers are arranged in cymes. A cyme is an inflorescence in which  each growing point ends in a flower, with new flowers coming from side shoots. The oldest flowers are at the top: seen going to fruit here (note the buds towards the bottom).