One of the flowers you have to be able to recognise if you are in Dorset and have an interest in such things is the common centaury (Centaurium erythraea). It is frequently encountered both on calcareous soils and on acid too. You can find it on the grassy downs at places like Durlston and you can encounter it on the heaths, often by paths where the soil is sell worn and the vegetation is thin; it seems to like sandy, dry soils.
An attractive plant, it recalls gentian when you see it at first and it is indeed a member of a sub-order of the gentian family. The flowers are pure pink (occasionally white)and grow in small clusters of three or so at the top of each branch of the stem. Generally not growing very tall it can actually be only a couple of inches tall but is usually between six to ten inches, rarely bigger. The small leaves are in pairs at the junction of each stem branch.
There are six centaury species in my guide but two perennial do not occur in Dorset and another is yellow! Slender centaury only occurs on the under cliff near Lyme Regis and so you really only have a choice of two here. The only other possible centaury you could confuse it with is lesser centuary which has flowers that are deeper red, have more pointed petals and are smaller. The also occur on longer stalks making the flower head more open or fragmented. Lesser centuary is also quite rare here.
The origin of the name is unclear. The centaur was a mythical Greek creature which had a horse body but a mans upper body in place of a horse's neck and head, it was neither man nor beast. This plant bears no resemblance to that!