Monograph contain information on

The correct answer is any one taxon.

To understand why this is the correct answer, let's break down the definitions of various taxonomic aids:

1. Monograph: A monograph (derived from the Greek words mono meaning "single" and grapho meaning "to write") is a comprehensive taxonomic treatise that contains information on any one taxon (such as a family, genus, or species) at a given time. It details the systematic study of that particular taxon, including its characteristics, classification, keys, and evolutionary relationships.
2. Flora: A flora contains the actual account of habitat and distribution of plants of a given area. It provides an index to the plant species found in a particular geographical region.
3. Manuals: Manuals are useful in providing information for the identification of names of species found in an area.
4. Catalogues: Catalogues provide an alphabetical list of species found in a particular area, often with brief descriptions.

Therefore, while a flora describes the plants of a particular area, a monograph specifically focuses on detailing all available taxonomic information about a single, specific taxon (such as one family, one genus, etc.) across its entire geographical range.