I'm losing my touch with stained glass! I used to take beautiful pictures of stained glass windows, but today I just pointed my camera and clicked. I'll definitely go back and fiddle with the exposure so as to not get the blown-out light areas.
This is St. Agnes at Trinity Episcopal Church in Collinsville. She was a young virgin from a Christian family in late 3rd century Rome. A local prefect wanted her to marry his son, but she refused, and the prefect ordered her to be put to death. In those days, a virgin was not allowed to be executed (she was only 12 or 13), so the prefect dragged her to a brothel, but none of the men were able to deflower her. She was then ordered to be burned but would not burn; eventually she was killed by the sword.
She is the patron saint of gardeners (hence the flowers) and is always depicted with a palm frond (a symbol of martyrdom) and either holding a lamb or with a lamb at her feet. The lamb (Agnus in Latin) is part of her iconography because the word is so close to Agnes.
Here is a link to another St. Agnes window I photographed in Stamford CT. http://stjohns-stamford.org/parishlife/glass/martyrs/