Summary..Plants ofAgropyron repens(L.) Beauv. which bad been sprayed with N‐(1,1‐dimethylpropynyl)‐3,5‐dichlorobenzamide (pronamide) were examined for changes in external and internal morphology at various times after spraying. Cell enlargement, some necrosis, and an increase in nuclear volume characterized treated rhizome apices. Abnormal metaxylem vessel elements and necrotic phloem were characteristic of the rhizome vascular tissues. Roots showed precocious differentiation and maturation of tissues and eventual vacuolation of the apical maeristem, resulting in complete inhibition of root growth. Nuclei of root meristem cells were much enlarged and contained several nucleoli.Effets duN‐(1,1‐diméthylpropynyl)‐3,5‐dichlorobenzamide sur l'anatomie de l'Agroyron