Kate Greenaway 
Language of Flowers (Illustrated) [EPUB ebook] 

This revised kindle edition contains additional illustrations of flowers, captioned to include their meanings
A pretty book matching flowers and plants to their meanings. Listed in both in alphabetical order and in reverse order (matching meanings to plants/flowers) the book also contains many charming 19th Century illustrations.
A selection of flower-themed poetry is also included at the end of the book, eg. Daffodils (Wordsworth); The Rose (Waller); The Sensitive Plant (Shelley); Adonis Sleeping (Keats); The Daisy (Chaucer).
A useful reference book for exploring symbolism in nature.
Cowslip = Pensiveness. Winning grace.
Geranium, Lemon = Unexpected meeting.
Lily, White = Purity. Sweetness.
Primrose = Early youth.
Snowdrop = Hope.
Sweet Pea = Delicate pleasures.