According to the third stanza, why is the tree dear to the poet?

Like a huge Python, winding round and round
The rugged trunk, indented deep with scars
Up to its very summit near the stars,
A creeper climbs, in whose embraces bound
No other tree could live. But gallantly
The giant wears the scarf, and flowers are hung
In crimson clusters all the boughs among,
Whereon all day are gathered bird and bee;
And oft at nights the garden overflows
With one sweet song that seems to have no close,
Sung darkling from our tree, while men repose.

When first my casement is wide open thrown
At dawn, my eyes delighted on it rest;
Sometimes, and most in winter,—on its crest
A grey baboon sits statue-like alone
Watching the sunrise; while on lower boughs
His puny offspring leap about and play;
And far and near kokilas hail the day;
And to their pastures wend our sleepy cows;
And in the shadow, on the broad tank cast
By that hoar tree, so beautiful and vast,
The water-lilies spring, like snow enmassed.

But not because of its magnificence
Dear is the Casuarina to my soul:
Beneath it we have played; though years may roll,
O sweet companions, loved with love intense,
For your sakes, shall the tree be ever dear!
Blent with your images, it shall arise
In memory, till the hot tears blind mine eyes!
What is that dirge-like murmur that I hear
Like the sea breaking on a shingle-beach?
It is the tree's lament, an eerie speech,
That haply to the unknown land may reach.