Abstract
Nine of the 36 spp. of plants studied showed positive pollen tube chemotropism to their respective pistil part or parts under the specified exptl. conditions. The active factor in both Antirrhinum and Hippeastrum was shown to be a slowly diffusing, heat-stable, water-soluble substance of considerable molecular size. Of all the pure substances tried, none showed any effect in attracting or repelling the pollen tubes of any species. The active factor in the stigma of Lilium superbum was shown to diffuse out from the tissue into an agar block. The chemotropism of pollen tubes was shown to be related to the developmental stages of the flower. It also seemed to vary with some undetd. internal or external factors.
Keywords