Step 1: D. Chatterjee (1962) divided the flora of India into nine phytogeographical zones based on distinct floristic composition.
Step 2: These nine zones are Eastern Himalayas, Western Himalayas, Assam, Indus plain, Gangetic plain, Central India, Deccan, Malabar (west coast), and the Andaman Islands.
Step 3: Eastern Himalayas, Gangetic plain and Central India all appear directly in this list.
Step 4: South-East India is not one of the nine named zones, so it is the one not mentioned.