The fruit of the rose is a berry-like structure called a rose hip. The hips of most species are red, but a few (e.g. Rosa pimpinellifolia) have dark purple to black hips. Each hip comprises an outer fleshy layer, and inside containing 5-25 seeds (technically achenes) embedded in a matrix of fine, but stiff, hairs. Rose hips of some species, especially the Dog Rose (Rosa canina) and Rugosa Rose (Rosa rugosa), are very rich in vitamin C, among the richest sources of any plant. The hips are eaten by fruit-eating birds such as thrushes and waxwings, which then disperse the seeds in their droppings. Some birds, particularly finches, also eat the seeds