Velimir, sometimes on the straw roofs planted the Natresk plant or the netskin that you have on the photo. This plant, as the name suggests( ne tresk not tremble), protects the house and people from lightning strikes. At the same time this plant is greatly heal Warts (bradavice) I do not know how to say it in English. Tear off a leaf from the plant and squeeze a drop of juice. Do this for days and they will disappear. The best is because they do not smell and have no color