Answer:
“imaginary gardens with real toads in them,”“literalists of
the imagination”, "When they become so derivative as to become unintelligible", to discriminate against “business documents and school-books”
Explanation:
This verse is one poetic picture where we can imagine a beautiful garden with flowers and trees and among them toads. There is a metaphoric picture where we can see the opposition between what we imagine when we read the garden and what the writer wrote in this verse. Authentic thought is to put something which people connected with ugly and not to put with something beautiful. The writer shows us how to be innovative and also tell people who criticized his poetry that he is full of imagination and new ideas.
Also one of the ideas in this poem is that poets can be a prisoner of imagination(“literalists of the imagination”) which means that they can not always write about the imagination, they should include in their poetry reality. They should try to write verses and rewrite verses if is necessary, not just to rhyme verses.
The poetry should express authentic ideas which are explained in verse "When they become so derivative as to become unintelligible". He criticized poets who want to show all the beauty of their poetry and all their skills so their verses are unintelligible.
The poetry can not express feelings when business documents and school books are the subjects. There are important for life, and poetry is here to explains and evokes life.