POLLEN germination involves the conversion of the quiescent vegetative cell into a metabolically active and rapidly growing pollen tube1. Although many external factors influence pollen germination, no predominant control mechanism has been identified. In certain lymphocytes in culture, lectins (plant agglutinins) have been shown to stimulate quiescent cells to enlarge and synthesise DNA2,3. Lectins also bind to the surface of actively growing cells and cause agglutination of red blood cells and transformed or malignant cells2–4, of gametes of Chlamydomonas5 and of carrot protoplasts6. There have, however, been few studies of the effects of lectins on plant tissues. The results presented here show that the lectins, concanavalin A (con A) and phytohaemagglutinin-M (PHA), stimulate pollen of Lilium longiflorum to germinate more rapidly than controls, by reducing the length of the lag period before pollen tube emergence.