"This credo, which placed the demands of practical use above aesthetics, later would be taken by influential designers to imply that decorative elements, which architects call "ornament", were superfluous in modern buildings, but Sullivan neither thought nor designed along such dogmatic lines during the peak of his career.While his buildings could be spare and crisp in their principal masses, he often punctuated their plain surfaces with eruptions of lush Art Nouveau or Celtic Revival decorations, usually cast in iron or terra cotta, and ranging from organic forms, such as vines and ivy, to more geometric designs and interlace, inspired by his Irish design heritage.