The Poas have adjusted themselves to contrasting climates from warm temperate to high arctic regions of both the Northern and the Southern Hemispheres. Their bipolar distribution would suggest great geologic age, but they nevertheless have preserved evolutionary youthfulness through polyploidy and apomixis. Transfer of large blocks of heredities between long separated groups of species is accordingly possible without causing disaster to their reproductive mechanism by seed. The Poas have not yet reached the limits of their potential to exchange heredities between species that belong to taxonomically distinct sections, between species of separate continents, and between species of the Northern and the Southern Hemispheres which have remained apart since early geologic periods.