Cut stone and brick masonry allowed much diversity in the decorative treatment. In its simplest form a single brick marks each of the vertical and horizontal joints. In the twelfth century church of the Koimesis at Chonika, Argolis (upper left), the monotony is relieved by introducing a cross, consisting of large blocks rising through nine courses of masonry, on either side of the door. A legacy of the Arab invasions is the ornamental Cufie writing which formed the basis of many decorative patterns in Byzantine art. Single units, intermingled with Christian symbols, were used to separate blocks in Winter 1952 the church of the Holy Apostles in Athens (upper right), dating from the early eleventh century. In the probably contemporary church of the Panagia at Hosios Loukas (lower left) further elaboration was achieved by the multiplication of bricks in the horizontal courses and by the use of whole courses of continuous Cufie ornament. In northern Greece particularly the regular masonry was frequently interrupted by broad stretches of brick work set in a variety of geometric patterns, as in the thirteenth century church of the Panagia Olympiotissa in Elassona (lower right), southern Macedonia. 243