The earliest use of the lily by the artists of the Christian Church was to indicate the delights of Paradise. Raban Maur, Archbishop of Mayence in 847, writes of lilies as the symbols of celestial beatitude, and that is apparently what they represent in the mosaics of Rome, Ravenna and the Baptistery of Florence, where they spring from the ground in the scenes which represent Heaven. But by the tenth century the Church had commenced to adopt the pre-Christian employment of the lily as the symbol of purity, and the rose gradually took the lily’s place as the flower of heavenly bliss. The lily of sacred art is the _lilium candidum_, sometimes called the Madonna lily, or the lily of Saint Catharine. It is said to be a native of the Levant, but appears to have spread with Roman civilization throughout Europe. The suggestion of abstract purity is arresting and direct. The stalk is straight and upright, the leaves narrow, plain, almost austere. At the top of the long stalk the flowers cluster, each chalice-shaped, and sending to the sky a perfume which is singularly sweet and piercing. Their form is simple but noble, and they are above all remarkable for the immaculate and luminous whiteness of their firm petals. After the twelfth century the lily is always used as the symbol of purity in its perfection, and is most usually associated with the Virgin Mary and with saints of the monastic orders. More rarely it is used as an attribute of the Persons of the Holy Trinity. In a large picture[10] representing the Trinity in Glory, by an unknown Neapolitan painter of the seventeenth century, God the Father holds a stalk of lilies in his left hand, above which hovers the mystic Dove. Since Christian iconography gives no attributes to God the Father except the orb and crown of omnipotence, the lily must be taken as the attribute of the Holy Ghost; and in a rare subject, The Adoration of the Holy Ghost,[11] ascribed by Behrenson to the _Amico di Sandro_, the two angels with swinging censers and lovely floating draperies, who adore the hovering Dove, carry each a lily. The Dove in conjunction with the lily is also found upon the great central doors of Saint Peter in Rome. They are of bronze, and were executed between 1439 and 1445 by Antonio Filarete. There are two panels with elaborate borders and much interesting detail. On one is Saint Peter with the keys and on the other Saint Paul. Saint Paul is of the traditional type, bald and bearded, and holds in his right hand a drawn sword. By his side is a large vase of lilies, and on the highest flower, its beak touching the sword’s hilt, is the Dove, encircled by a halo. The lilies and the Dove are introduced apparently to correct the impression of violence given by the uplifted sword, the instrument of the Apostle’s martyrdom, and together representing the Holy Spirit, they recall Saint Paul’s own phrase, ‘the sword of the Spirit.’