AEstivation (from the Latin erstivus, "belonging to summer"), the term applied in botany to the folding of the floral leaves, or sepals and petals in the flower-bud, such buds being mostly produced in summer. It is a character of importance as serving to distinguish some of the natural orders of flowering plants. The folding or rolling of the leaves individually, and their collective arrangement have to be separately considered. Individually they may be reclinate, their apex folded to their base; conduplicate, their two sides folded together; plicate, folded like a fan; convolute, rolled up from one side, like a scroll; involute, with their margins rolled inwards or upwards; revolute, with the margins rolled backward; circinate, rolled up from apex to base, as in the petals of Hamamelis; or crumpled, as in those of poppies. Collectively they may be valvate, meeting at the edges without overlapping, as in the sepals of Clematis or of the Malvacem and the petals of the vine (Vitis); or imbricate, overlapping one another. Among varieties of imbricate aestivation, the chief is that known as contorted, where one edge of each leaf is rolled over the next, as in the petals of Malva.