The changeover was complete; in the summer of 1907 I devoted myself entirely to the appearance of nature and upon these studies built my black-and-white landscapes on glass, 1907/1908.
Source, in full
Quote (1908), # 831, in The Diaries of Paul Klee; University of California Press, 1964; as quoted by Francesco Mazzaferro, in 'The Diaries of Paul Klee - Part Three' : Klee as a Secessionist and a Neo-Impressionist Artist