Icones 19 is the first of four parts to treat the genus Masdevallia. It begins with a 10-page introduction to the genus with a key to the subgenera and sections. It follows the basic concept outlined Icones 2, but with significant revisions. Part One consists of only one subgenus (Polyantha) of two sections (Alaticaules and Polyanthae), which altogether contain 104 species, about one-fourth the total number in the genus. Each species is represented by text, descriptions, a distribution map, and at least one full-page illustration. Part One contains 264 pages with 132 illustrations. For persons interested, a loose-leaf edition is also available, so that future rearrangements can be made, and additions and corrections can be easily inserted.