Two distinct groups of inclusions are recognized in the stroma of developing chloroplasts of mesophyll cells of aTriticale.One group, identified as fibrillar-globular inclusions, was studied in a former work (OLIVEIRA 1975b) and it is included here for discussion purposes. The second group is represented by inclusions which by the nature, dimensions and enzyme sensitivity of their elements are ribosomal. These ribosomes are organized into helical arrangements of polysomes. Deviations from this basic type of organization occur, but such variants may be due to planes of sectioning of the polysomes. Beside theii structure, the present work discusses the possible significance of the presence of these polysomes in terms of their ability to perform protein synthesis.