Summary.A laboratory method is described for studying the effects of introducing herbicides into the vascular tissues oiPopuluscuttings. Of sixteen herbicides tested in this way, MCPA and picloram were the most phytotoxic. Ester formulations of growth regulator herbicides were less active than water soluble amine or inorganic salts. The phytotoxic effects of the latter were increased by supplying water to the cuttings before or after treatment or by applying the herbicide in a relatively large volume of water. A non‐ionic surfactant did not increase the effects of injected MCPA salt, approximately similar amounts of which moved both upwards and downwards in cuttings from the point of introduction.Expériences en laboratoire sur des boutures dePopulus × euroamericana“I‐78” traités avec des