- In the 15th and 16th century Spanish missionaries adopted the symbols of the plant as parallels to Christ's last days on Earth, so the word "passion" refers to the Passion of Jesus Christ.
- All flowers have 10 petals that represent the apostles (minus Judas Iscariot and St. Peter)
- The 3 stigmate represent the 3 nails used in hands and feet.
- The 5 anthers represent the 5 wounds (2 hands, 2 feet, and the lance wound in the ribcage)
- The filaments represent the crown of thorns.
Here's a link to the Wikipedia page if you wish to read more on the Passion Flower.