Paul Klee used lines in three principal ways in his paintings and drawings: to draw patterns, to make letters, numbers and other symbols and to refer to the physical features of objects. M. L. Teuber (1976) has shown that at different periods of his life Klee varied the way in which he used lines to refer to physical features. During the period 1925–1931, in the Bauhaus group at Dessau, Germany, for example, he used lines to suggest the transparency of overlapping planes.
Recent work in the field of digital computers has revealed the existence of systems of ‘rules’ that underlie the ways in which lines can refer to physical features. One rule that is common in such systems is that a line should refer to the same feature throughout its length, and this is a rule that Klee often violated.
During the last two years of his life, Klee produced a number of paintings and drawings in which lines represent the bounding contours of smooth forms. A method is described for analyzing such pictures. When these pictures by Klee are analyzed, digressions from the rules are revealed. It is argued that in many cases Klee deliberately introduced such digressions to obtain expressive effects and that these effects are appropriate to the subject matter of the pictures.