Which is the largest botanical garden in the world? Name a few well-known botanical gardens in India.

(N/A) $\rightarrow$ The largest botanical garden in the world is the Royal Botanical Garden,Kew (London).
$\rightarrow$ Some well-known botanical gardens in India are:
$1$. Botanical Garden,Vaghai (District Dang,Gujarat)
$2$. National Botanical Research Institute $(NBRI)$,Lucknow (Uttar Pradesh)
$3$. Acharya Jagadish Chandra Bose Indian Botanic Garden,Shibpur (Kolkata)
$4$. Lloyd Botanical Garden,Darjeeling (West Bengal)