Yew tree berries. Historical artwork of the red berries and green leaves of a yew tree (Taxus baccata). The red part of these berries (the aril) is the only non-poisonous part of the yew tree. The rest of the plant contains a swiftly acting, heart-paralysing alkaloid called taxine. Birds can eat the berries safely as the poisonous seeds pass through them undigested. The yew gains from this arrangement as the birds unwittingly disperse the seeds over wide areas, fertilising them with their dung. From The Instructive Picture Book or Lessons from the Vegetable World, Charlotte Mary Yonge, 1857.