The cytogeneticist John Belling (1866-1933) developed the iron-acetocarmine staining technique, which facilitated detailed study of chromosomal structures. In his work with Arthur F. Blakeslee at Cold Spring Harbor on Datura (1920-1927) and at the University of California, Berkeley (1928-1933) on lilies, hyacinths, and other plants, Belling made accurate estimates of chromosomal numbers, helped to demonstrate the interchange of segments between non-homologous chromosomes, and proposed that the chromomeres (small condensations of stain that appeared along the length of chromosomes) represented individual, physical genes. Although he was a gifted technician and insightful cytologist, his career was hampered by mental instability and curtailed by frequent hospitalizations before his sudden death in 1933. The Belling Collection consists of four photograph albums, 38 glass slides and approximately 75 glass negatives and positive prints of chromosome preparations made by Belling, primarily during the years at Berkeley, along with an annotated bibliographic card file. The images in the albums are fully identified, but most of the glass slides are not.