The vascular bundle sheath chloroplasts of japonica-2 maize plants are characterized by (1) a slower rate of plastid morphogenesis, slower even than in the mesophyll cells, and slower in the pale green tissues than in the dark green ones, so that the chloroplasts of the pale green tissues never reach the final developmental stage; (2) by a constant, often sharply marked, swelling of thylakoids, until the final stage; (3) by the complete failure to accumulate starch grains until the final stages, and (4) by the lack of typical structures in the young cells, e.g. the small crystalline prolamellar bodies. The possible events which cause these phenomena are discussed.

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