What is a monograph?

Hint: Organisms are classified and arranged based on their characteristics. The monograph represents the detailed study of the organism including its important characters that were used to classify it. This is used for identification purposes as well as to study various aspects of the organism.

Complete answer: A monograph is defined as a systematic detailed study of a particular organism or its taxonomic group. This is a detailed analysis of characteristic features of the given organism. It is a detailed comprehensive study that relies on the given taxon or taxonomic group. The taxa is the rank given to the particular organism level. A monograph does not consider the geographical distribution of the organism. It takes into account the descriptive features and characters of an organism or species. A monograph is made by reviewing all of the present species within is a group. Whenever an organism is discovered and needs to be placed in a particular taxon, the monographs are reviewed.
Monographs are used to form or to collect available information based on the ecological associations and morphological variations present within the given group of organisms. It is a form of specialized writings or reviews relating to a single aspect of a specific object, especially the taxonomical aspect. A monograph is also described as a study branch dealing with the study of taxon without relating to their geographical distribution.
A monograph provides key descriptions of a species along with correct nomenclatures. It takes into account the embryology, evolutionary history, and reproductive biology of the species. In the case of plants, a monograph also considers pollination and seed dispersal. Monographs are written after very detailed and extensive research and thus require focus and interest to write it.

Note: Robert Morison created the first-ever monograph named Plantarum Umbrella Ferarum Distribution Nova. The Apiaceae group of organisms is studied and described in detail in this monograph. A vast amount of information about a specific organism can be found from a monograph.