Plants in the euphorbiaceae, or spurge family have (mostly) simple, alternate leaves and small, inconspicuous flowers, either male or female, in both of which the corolla and calyx are divided into five lobes. The Bristish Isles has two species in the mercurialis genus and 15 in the euphorbia genus; for the latter, the flower has a specialised structure, a cyathium, formed of fused bracts around a ring of stamens and nectar glands, with a pistil at the centre.