Nymphs | Dryad

Nymphs: three occurences, Dryad: one occurence.

Groves with strange flowers like eyes of gazing nymphs
     — Book 5 Canto 2

I have seen the wood-nymphs peering through the leaves;
     — Book 5 Canto 3

Here are not happy peaks the heaven-nymphs roam
     — Book 6 Canto 1

Invisibly protected from our sense
The Dryad lives drenched in a deeper ray
And feels another air of storms and calms
And quivers inwardly with mystic rain.
     — Book 4 Canto 1

In Greek mythology nymphs are personifications of the spirits of nature. Nymphs were considered to be deities of a lower rank.

Dryads are a category of nymphs specifically related to trees.

Sri Aurobindo uses this word in the canto The Birth and Infancy of the Flame to explain that the sensations related to perceptions of the powers of nature change.