This bonnet is a style known as a 'capote' bonnet. It was worn at a forward angle on the crown of the head with the wearer's hair piled up high underneath. The bonnet was held on by the ribbons which tied in a large bow beneath the chin.
This period in the later 19th century saw a craze for all forms of embellishment on dress and accessories, of which this hat is a great example. The diverse decorations include a decorative straw plait hood which is overlaid with lace, then trimmed with large pleats of velvet, adorned with silk poppies and finished with a brocaded ribbon.