Hatch and Slack discovered another alternative pathway for CO2 fixation called as Hatch and Slack cycle. This cycle is found in. C4 plants. C4 plants shows a special type of leaf anatomy. Known as Kranz anatomy, which is characterised by the presence of large agranal chloroplast in the bundle sheath cells and small granal chloroplast in mesophyll cells. C4 cycle or Hatch and Slack cycle takes place in bundle sheath cells and C3 cycle or calvin cycle takes place in mesophyll cells.