Each Hail Mary was intended to be a spiritual rose

The prayer of the Rosary was not finalized overnight. At first the Christians wanted to greet Mary with the words that the Archangel Gabriel pronounced at the Annunciation: "Hail Mary, full of grace," with Elizabeth’s blessing: "You are blessed among all women." The second part, "Holy Mary, Mother of God," was only added in the 15th century.

Each Hail Mary was intended to be a rose, which helped form a small crown ("rosary"). At first the number of Ave Marias (150) matched the number of psalms (150) in the Bible. A small string of beads helped keep track of the number of invocations recited.

The rise in popularity of the Rosary is due to the Dominicans, especially Brother Alain de la Roche in the 15th century, who had the idea of founding a brotherhood of the Rosary... Since the Dominicans are an order of preachers, they associated a "mystery" – a significant moment in the life of Christ – to each decade (10 Hail Marys), also highlighted by the life of his Mother who was his close associate. Therefore the mysteries range from her first Fiat to her Coronation in glory. In praying the Rosary, we are asking Mary to bring us into communion with Jesus Christ, her Son.

Bishop Jacques Perrier, former bishop of Lourdes

October 7, 2013 Zenit.org