Final answer:
Horsetails, also known as Scouring Rushes, have hollow, ribbed stems embedded with silica, making them abrasive. They were historically used as natural scrubbing tools for cleaning. Photosynthesis in horsetails occurs mainly in the stems, rather than the leaves.
Step-by-step explanation:
Horsetails, belonging to the genus Equisetum, earned the nickname "Scouring Rushes" from a unique characteristic of their stem. These plants have hollow, ribbed stems that are coated with the mineral silica, making them rough and scratchy. This is because silica is deposited within the cell walls of the stems, making them abrasive enough that they were historically used as scrubbing brushes for cleaning dishes, lending them their colloquial name.
Horsetails are interesting plants as they can conduct photosynthesis primarily in their stems due to the needle-shaped leaves not contributing greatly to the process. They have a distinctive jointed stem, and their appearance once led people to use them as a tool for scouring or cleaning, which is not a common trait among plants. Today, horsetails may be found in wet habitats such as marshes and are known for their medicinal and pest controlling properties, although their abrasive stems are no longer commonly used for cleaning purposes.