Friedrich Ritter (1898-1989)

Under copyright
This book is still under copyright. In spite of our efforts it has been impossible to find any interested party. The book is nevertheless proposed owing to its historical interest. A reprint is unlikely since Ritter published the book himself. However, if you can help solving the ownership problem, please contact us.


The book was edited from 1979 to 1981. It is made of 4 volumes, 1692 pages and 1416 illustrations. Friedrich Ritter presents his extensive field work throughout South America and his point of view about cactus classification. Even though the latter is now out of date, the field data and plant descriptions (including many latin diagnoses) are of high interest. Unfortunately, the illustrations are of very bad quality, most in B&W (from color originals!), and they are thus of limited help ¹⁾

• Read online in the reading room
• Download :
  • Interpreted file:
    • Volume 1: KaktSudam1.pdf (15.1MB; 2010-03-24) [Brazil, Uruguay, Paraguay]
    • Volume 2: KaktSudam2.pdf (22MB; 2010-04-28) [Bolivia, Argentina]
    • Volume 3: KaktSudam3.pdf (17.9MB; 2010-08-17) [Chile]
    • Volume 4: KaktSudam4.pdf (19.8MB; 2010-10-03) [Peru]
  • Original file:
    • Volume 1: KaktSudam1_O.pdf (102.4MB; 2010-03-24)
    • Volume 2: KaktSudam2_O.pdf (123.4MB; 2010-04-28)
    • Volume 3: KaktSudam3_O.pdf (106.1MB; 2010-08-17)
    • Volume 4: KaktSudam4_O.pdf (111.2MB; 2010-10-03)

Description of flower colors:
Ritter used the Pflanzenfarben Atlas of E. Biesalski to decribe the colours accurately. The chart is based on the German standard DIN 6164. A colour is defined by 3 numbers T, S and D:

1. The hue, T (for Farbton) is the reference colour (from yellow to green through red and blue).
2. The saturation, S (for Sättigung) defines the “strength” of the coulour. When S = 0, an image is in black & white.
3. The shadow (or darkness), D (for Dunkelstufe) defines the brightness. The higher D, the darker the colour (D = 9 is black).

The DIN6164_A0.pdf file gives a sample colour model and the associated T:S:D numbers.