The chloroplasts of sieve parenchyma cells from leaf minor veins ofArum italicumMill. are characterized by the presence of elongated paracrystalline inclusions often of very large size (up to 18–20 μm and over). Some sections of these inclusions clearly give evidence of a periodical structure. The thylakoidal system of these chloroplasts is well developed; the stroma is full of ribosomes often united into polysomes, which are frequently found attached to the external surface of thylakoidal membranes. A close spatial relationship between chloroplasts and dictyosomes is observed.