In which of the following do we store dry plants for information purposes?

The correct option is herbarium.

Step-by-step Explanation:

To identify where dried plants are stored for information purposes, let us look at the definition and function of each of the given taxonomic aids:

1. Herbarium: A herbarium is a storehouse of collected plant specimens that are dried, pressed, and preserved on paper sheets. These sheets are systematically arranged according to a universally accepted system of classification. They carry labels containing information about the date and place of collection, English, local, and botanical names, family, and the collector's name. It serves as a quick referral system in taxonomic studies.

2. Monograph: A monograph is a detailed and comprehensive written account or treatise on any one taxon (such as a specific genus or family). It is a publication, not a physical storage facility for dried plant specimens.

3. Museum: Museums generally maintain collections of preserved plant and animal specimens for study and reference. These specimens are often preserved in containers or jars using chemical solutions, or kept as dry specimens (such as stuffed animals or insects in boxes). While biological museums do store plant specimens, the dedicated repository specifically designed for storing dried, pressed, and cataloged plant sheets is a herbarium.

4. Key: A key is an analytical taxonomic aid used for the identification of plants and animals based on similarities and dissimilarities. It consists of contrasting statements, rather than physical specimens.

Therefore, dried plant specimens are stored for taxonomic studies and information purposes in a herbarium.