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Fritsch Sheets
 Fritsch Collection layout
How the  Fritsch Collection is organized
For ease of reference the individual sheets were, and still are, organized alphabetically by genus and species within the major algal groups: Chlorophyta; Bacillariophyta; Cyanophyta;Chrysophyta; Rhodophyta, Phaeophyta; etc.  Some Bacteria are also filed. These are housed in 4-drawer filing cabinets which hold about 2000 in each drawer.
Sheets are each headed with species name and authority, every entry includes the author and date to link to the author reference.  Errors in information are constantly being corrected as the initial entry did not always come from the original authority and misinterpretations have occurred over time. Cross checks are made with the original publication, and to Index Nominum Algarum and AlgaeBase
Most of the sheets of Prof. Fritsch’s original collection include cross-references to related species, and  notes and descriptions attached as overlays.
Subspecies,varieties and forms are also included on the species sheet, with author and date.
Today the original species diagnosis is included with the illustration.  Although the majority of species feature on just one sheet, well known species fill several whilst the dinoflagellate Ceratium hirundinella covers 99 sheets.
Fritsch Sheets
 Fritsch sheets

Over time species have been reclassified as our taxonomic undestanding has increased. However, species sheets are very rarely renamed or refiled following reclassification, or if so this is made obvious in the heading. The rationale is that the entry is cross-linked to the literature which includes that name, not a new combination. New sheets with the new cominations or status are usually linked to the earlier name.
There is a genus index with details of authority and type, and the cross-reference to the location of the group.
All the author references are card indexed and about one third is searchable online – see Author References.