With the use of stigmatic exudate or distilled water as carriers, various antimetabolites, inhibitors, and miscellaneous materials were injected into the hollow styles of detached Lilium longiflorum pistils before, at, or after compatible or incompatible pollination. Pollen tube lengths were measured 48 hr after pollination with pollinated styles incubated at 22-23 degrees C. Substances considered inhibitors of protein synthesis in microbial systems significantly retarded both compatible and incompatible pollen tube growth while inhibitors of RNA synthesis tended to significantly inhibit compatible pollen tube growth with less or no effect on incompatible pollen tubes. Application of the inhibitors in stigmatic exudate at or after compatible pollination produced significant results at the lowest concentrations. Significant retardation of pollen tube growth also occurred after injection of 2,4-dinitrophenol, mercaptoethanol, indoleacetic acid, naphthaleneacetic acid, benzyladenine, dimethyl sulfoxide, or potassium or sodium iodide. Pollen tube growth in detached pistils of L. longiflorum may be useful as a bioassay in situ for screening biologically active materials.