Pollination in Early Purple Orchid, Orchis mascula. The picture shows an open flower of O. mascula, and the tip of a pencil. The pencil has been pushed into the flower and then withdrawn. Attached to it (picture centre) are two masses of pollen, called pollinia. The pollinia are arranged at the end of short stalks, which have a strongly adhesive base. The picture illustrates how the plant ensures cross-pollination. Open flowers are visited by bees. The bee pushes itself into the flower, seeking nectar. It then flies to neighbouring plants, bearing pollinia glued to its thorax. During the flight, the stalks bearing the pollinia loses turgor, and the pollinia fall forward. In this position they contact the receptive female surface of the next plant. Ingenious pollination mechanisms are widespread among orchids. The method used by O. mascula was first described by Charles Darwin in 1862.