If I should die
gurgle on
Weird verb choice—time doesn't gurgle. It's mock-cheerful, like baby talk, undercutting the serious premise with bathos.
depart at option
Suicide hint. If nature keeps going without you, why stick around? The business language ('option,' 'enterprise') makes death sound like quitting a job.
stocks will stand
Double meaning: flower stocks in the garden AND stock market shares. Death becomes a financial matter.
gentlemen so sprightly
Savage irony. These cheerful businessmen conducting life's 'pleasing scene' are oblivious to individual death—or she's mocking the idea that this should comfort anyone.