SUMMARY OF THE MOST IMPORTANT RESULTS (quoted from the book): During three decades of the present century (1920-1950) Krasske was an important author in the field of diatom research, viewed from the geobotanical and taxonomic perspective. Altogether 270 descriptions of new taxa from Central-Europe, Scandinavia, the Arctic, Asia Minor and South America were counted. It might be that his 123 taxa from South America are of special interest because comparatively little is known about the diatom flora of this continent. This documentation contains the protologues (including figures) of all the taxa introduced by Krasske. Moreover, all these taxa - so far as available in his collection- are represented by new microphotographs of the holotypes, lectotypes and/or other specimens from the type-slides or other authentic slides. Photographs are necessary since his diagrammatic figures are mostly of poor quality, and are therefore less significant. Many are hardly appropriate to recognize the depicted taxa. Attention! The indicated magnifications of the drawings are the original ones given by Krasske. They are not correct in several cases, corrections are provided. In addition, some illegitimate taxa introduced by Krasske under manuscript names have been photographed. In several cases taxa or specimens, which have not been taken from Krasske's collection, are shown for comparison. Another aim of this monograph is to evaluate Krasske's taxa critically from the contemporary and likewise from the recent point of view (see "Zusammenfassung", p. 187). In particular, it is shown how many of his types (names) represent "biologically" confirmed taxa. We consider 152 worthy of belonging to this category. The taxa are arranged alphabetically with the generic, specific and infraspecific names originally given by Krasske. However, the genera are mostly arranged on the plates in "classical fashion" by Hustedt and other authors, and not alphabetically. Exceptionally, the centric genera and Eunotia are placed at the end of the plate series. Three species and one variety are described as new taxa. ALLGEMEINER TEIL: Summary of the most important results/ Excerpt from the obituary by Hustedt 1952/ Introducción/ Extracto de memoria de Krasske, Hustedt 1952/ Einleitung (Auszug aus dem Nekrolog von Friedrich Hustedt 1952/ Verzeichnis der Veröffentlichungen Georg Krasskes/ Kurze Zusammenfassung der wichtigsten Ergebnisse)/ Material und Methoden (Die Collection Krasske/ Bemerkungen)/ SPEZIELLER TEIL: Protologe und Bemerkungen zu den einzelnen Taxa (S.24 - 186)/ Zusammenfassung/ Literaturverzeichnis / Bildtafeln/ Nachtrag/ Index.