Introduction:
In the Paper I of UPSC Botany Optional subject, referring to botanical gardens and herbariums can provide practical examples and enhance the understanding of the subject. Botanical gardens and herbariums are important resources for studying and researching plants, providing access to a wide variety of plant species and specimens.

Botanical Gardens:
Botanical gardens serve as living museums of plants, showcasing diverse plant species from around the world. They are designed to display plants in their natural habitats or in specialized gardens that represent different ecosystems. Here are some ways in which botanical gardens can be used as practical examples in Paper I:

1. Taxonomy and Classification: Botanical gardens provide an opportunity to study and observe plant taxonomy and classification. The various plant species displayed in botanical gardens can be analyzed based on their morphological characteristics, helping in understanding the principles of plant classification.

2. Plant Diversity and Conservation: Botanical gardens often have collections of rare and endangered plant species, contributing to their conservation efforts. The study of these collections can provide insights into plant diversity and the importance of conservation practices.

3. Medicinal Plants: Many botanical gardens have sections dedicated to medicinal plants, showcasing their importance in traditional and modern medicine. These gardens can be used as practical examples to understand the medicinal properties, uses, and cultivation techniques of various plant species.

Herbariums:
Herbariums are repositories of dried plant specimens that are stored, cataloged, and made available for scientific study. They serve as valuable references for plant identification, research, and documentation. Here's how herbariums can be useful in Paper I:

1. Plant Identification: Herbarium specimens provide a reliable means of plant identification. They consist of pressed and dried plant parts, such as leaves, flowers, and fruits, along with detailed information about the plant's habitat and distribution. These specimens can be referred to for accurate identification of plant species.

2. Plant Anatomy and Morphology: Herbarium specimens can be used to study plant anatomy and morphology. By examining the preserved plant parts, one can gain insights into the internal structures, tissue organization, and external features of plants.

3. Plant Distribution and Biogeography: Herbarium collections often include specimens from different regions, documenting the distribution of plant species. The study of these specimens can provide practical examples of plant distribution patterns, biogeography, and ecological adaptations.

Conclusion:
Referring to botanical gardens and herbariums in Paper I of UPSC Botany Optional subject can greatly enhance the practical understanding of various aspects of plant biology. These resources provide real-life examples, facilitating the application of theoretical knowledge to practical scenarios. By utilizing botanical gardens and herbariums, candidates can develop a more comprehensive understanding of plant taxonomy, diversity, conservation, anatomy, morphology, and distribution, thereby strengthening their preparation for the examination.