Rose sepal hairs. Coloured scanning electron micrograph (SEM) of the surface of a sepal in a Garden Rose flower Rosa sp. , showing hairs. Two types of hairs (trichomes) are visible projecting from the epidermal surface of the sepal. Numerous simple hairs are seen, unbranched and unicellular. A pair of larger, erect, multicellular hairs are visible with bulbous tips. These larger hairs are associated with secreting protective chemicals against pest attack, particularly when the plant is young. The sepals (calyx) form the tough outer whorl of the flower, surrounding the more delicate petals. They enclose and protect the flower when in bud. Magnification: x63 at 6x9cm size. magnification: x200 at 12x27cm size.