The symbolic use of lilies in mythology and literature is well-established.
Some notable examples follow:

Lilies in Greek and Roman mythology

The lily was a symbol of the Greek goddess Hera (Roman: Juno), again showing purity and innocence. One tale tells of lilies springing up from drops of milk spilled from Hera’s breast as she nursed Heracles. Another tells a story of how the lily acquired its pistil: as Venus rose from the ocean, she saw a lily and, jealous of the beauty of the pure-white flower, created an ugly pistil that came up from its center, thereby marring its beauty. This story accounts for the lily’s additional association with fertility and eroticism. Lilies were associated with death as well, signifying that in death, one regained one’s lost innocence and purity.

References:
Heart, S. F. (1997-2010). "The lily." Retreived from http://www.sfheart.com/lily.html.
Venefica, A. (2005-2010). "Lily meaning and symbolism." Retrieved from http://www.whats-your-sign.com/lily-meaning.html.

The Fleur-De-Lis
fleur-de-lis.jpg

The fleur-de-lis has long symbolized purity and divinity. Said to have grown from the tears Eve shed as she left Eden, the lily, especially white lilies, were symbols of the Virgin Mary, purity and innocence, and the trinity (due to its three-petaled shape). One legend tells that the Virgin Mary gave lilies to Clovis, the 3rd-century king of the Franks, at his baptism; this tale was used by French churchmen later to prove the succession of French monarchs. In another tale, that of Berta of Hungary, a coat-of-arms with the fleur-de-lys is bestowed as an honor on the family who took in the Queen Berta as one of their own, even though they did not know who she was, and helped her preserve her honor and purity. In AD 800, the pope supposedly presented the emperor Charlemagne with a banner showing golden lilies on a blue background. Thereafter, the fleur-de-lis was used, especially in France, to signify divine right. Today, the fleur-de-lis is commonly seen as a symbol of France and of French-speaking nations or provinces.

References:
Baronage Press and Pegasus Associates, Ltd. (1999). "The fleur-de-lis." Retreived from http://www.baronage.co.uk/bphtm-02/moa-15.html.
"Fleur-de-lis Christian symbol." (2008). Retreived from http://www.catholic-saints.info/catholic-symbols/fleur-de-lis-christian-symbol.htm.

Photo source:
Reynolds, L. (2005). "Fleur-de-lis." Retreived from http://www.flickr.com/photos/lwr/13396599/.


Lilies in literature


William Blake

To some critics, the lily in Blake’s poems and engravings represents not only innocence and purity of love, but also the promise of future heavenly reward. Blake’s Lilly contrasts with the other flowers represented in his Songs of Innocence and Experience to represent purity not yet marred. On the other hand, some read the poem in context as questioning what kind of “love” the lily represents: a “pure” love akin to the repressive “love” of the Church, or a more ostentatious, but sincere and open, genuine desire?

Reference:
Leader, Z. (1981). Reading Blake's Songs. Retreived from: http://books.google.com/books?id=z7Q9AAAAIAAJ&pg=PA167&dq=the+lily+william+blake&hl=en&ei=UYj0S9mfLISBlAf--O35DA&sa=X&oi=book_result&ct=result&resnum=6&ved=0CEoQ6AEwBTgK#v=onepage&q&f=false.


Emily Dickinson

Much has been written about the meaning of lilies to Emily Dickinson’s poetry. Dickinson wrote many times of admiring lilies in her garden, including a mention that the only commandment she followed was to “consider the lilies.” She and her sister named themselves after lilies that they were familiar with: her sister, a pond lily, and herself, a cow lily (which is what we would call an orange daylily). In her poem “Through the Dark Sod—as Education--” Dickinson used a lily (that most interpret as a calla lily) as a metaphor for the development of the soul.

Reference:
Farr, J., and Carter, L. (2004). The Gardens of Emily Dickinson. Retreived from: http://books.google.com/books?id=tK8nnFJ-KxUC&printsec=frontcover&dq=the+gardens+of+emily+dickinson&cd=1#v=onepage&q&f=false.


William Shakespeare

Perhaps the most famous literary quote about lilies is from Shakespeare: “To gild refined gold, to paint the lily,/….Is wasteful and ridiculous excess.” --King John, iv, 2

Shakespeare also several times used lilies as examples of purity or whiteness (particularly in the context of a beautiful complexion) with which to make comparisons, such as in sonnet 99, when he explains that he would scold the lily for stealing its whiteness from a lady’s hand. Frequently, notably, Shakespeare’s usage of lilies to conjure up images of whiteness or purity is juxtaposed with roses for blushing reds.


Reference:
Shakespeare, W. (1906). The sonnets. Retrieved from: http://books.google.com/books?id=twAoAAAAYAAJ&printsec=frontcover&dq=shakespeare+sonnets&cd=1#v=onepage&q&f=false.



Katherine Mansfield


In Katherine Mansfield's most famous short story, "The Garden Party," the main character, Laura, is confronted by the juxtaposition of the luxurious, leisurely life of her upper-class family and the harsh realities of life as shown to her by the death of a working-class man who lived near her neighborhood. Laura's mother, Mrs. Sheridan, refuses to call off her garden party just because of the death of the man, but afterwards, she has the idea to send a basket with leftover sandwiches and food scraps from the party, which Laura takes down to the family's home. In the story, Mansfield describes an overabundance to excess of bright pink canna lilies ordered by Mrs. Sheridan, who says, "I thought for once in my life I shall have enough canna lilies." The group later suggests that Laura take some of the flowers (lilies) to the family as well, but it is mentioned that the stems would ruin her dress, and she only takes the basket of food. Some critics cite a typical symbolism of lilies as representing innocence, but others cite the excess (even by the standards of the upper-class Sheridans) of expensive flowers, and the selfishness of them in not sending any of the flowers to the funeral for the sake of Laura's dress, as an ironic symbol of the corruption and excess of the oblivious wealthy class

Reference:
Mansfield, K. (1922). The garden party, and other stories. Retrieved from: http://books.google.com/books?id=quRLAAAAIAAJ&printsec=frontcover&dq=the+garden+party&cd=2#v=onepage&q&f=false.