319 And bids this rare dispenser of your graces
dispenser > (Puns were a favourite literary device of the period: Spenser's own are usually subtler than this one)
320 Bow down his brow to her sacred hand.
sacred > {Commonly used (-1590) as an epithet of royalty; also, specifically, here, perhaps, because FQ traces Elizabeth's lineage back to Aeneas, whose mother was the goddess Venus}
321 Deserts finds due in that most princely doom,
Deserts > {That which in conduct or character deserves reward or
punishment}
doom > judgement, opinion
322 In whose sweet breast are all the Muses bred: 323 So did that great Augustus erst in Rome
Augustus > (Augustus Caesar, 63 BC-14 AD, Emperor of Rome, patron of
Virgil: on whom he is not, incidentally, known to have bestowed the
laurel crown)
erst > of old, formerly
324 With leaves of fame adorn his poet's head. 325 Fair be the guerdon of your Faery Queen,
guerdon > reward