The principle of attachment of pollen grains to flower-visiting insects is quite different in entomophilous angiosperms depending whether pollenkitt or viscin threads are the pollen adhesives. Pollenkitt is to be found in all angiosperm families investigated up to now, but viscin threads occur only in a small number. Moreover, the two pollen cementing principles do not correspond in their respective origin, structure, sculpture, and chemical and physical characters. Even the mechanical aspect of pollen cementing differs. Thus pollenkitt and viscin threads are analogous vehicles in pollination ecology.