Complex sentence: Their vascular bundles are surrounded by two rings of cells, the inner ring, called bundle sheath cells, contain starch-rich chloroplasts lacking grana which differ from those in mesophyll cells present as the outer ring.
Split into simpler sentences: Their vascular bundles are surrounded by two rings of cells. The inner ring, called bundle sheath cells, contain starch-rich chloroplasts lacking grana which differ from those in mesophyll cells present as the outer ring.