• http://www.sacredspiral.com/articles/ab/apple.htm

- Among the Celts, the fruit of the apple tree symbolized knowledge, magic, and prophesy. - When you cut the apple fruit breadthwise you see the five-pointed star made from the placement of the seed casings. This symbol, the pentagram, is the traditional symbol of knowledge. That the five-pointed star, pentagram, is surrounded by the circular shape of the halved apple, the symbol becomes a pentacle. This is a symbol of protection, the protection of sacred knowledge. - One custom regarding the apple fruit is to bury a few apples, after their harvest, to appease the spirits of the dead.

• http://paganwiccan.about.com/od/bookofshadows/ig/Pagan-and-Wiccan-Symbols/Pentacle.-0kj.htm

- Some cultures refer to the apple-star as the "Star of Wisdom", and so apples are associated with knowledge.

• http://www.scribd.com/doc/4986399/Wicca-The-History-of-the-PentagramPentacle
• http://www.religioustolerance.org/wic_pent.htm

- this link gives a lot of info on the pentacle from a pagan and christian historical perspective.