Periwinkle offers a lovely little flower, but it is the leaves and the seeds that are used in folk medicine. The leaves and seeds are rich in the chemical vincamine, an alkaloid that has positive effects on memory and has long been used to combat the effects of aging.eriwinkle is used in folk medicine in the Philippines as a remedy for diabetes. Most of these practices are still followed. Rosy periwinkle grows up to two and a half feet tall. Leaves are oval and have a glossy surface.
C4 envelopes are 229 x 324 mm in size and a A4 card blank can fit inside or an A3 card blank folded in half. These C4 envelopes are ideal for sending A4 documents or certificates. C5 envelopes are 162 x 229 mm in size and fit an A5 card blank or A4 card blank folded in half.
The dimensions of the C series envelope sizes, as defined by ISO 216, are given in the table below right in both millimetres and inches (cm measurements can be obtained by dividing the mm value by 10). The diagram below shows the size of each of the envelopes when compared to a sheet of A4 paper.