An application for a patent in the field of incandescent lighting covers, in essence, a light bulb. One of the limitations (elements) of the patent's principal claim is an "incandescing conductor of carbon made from a vegetable fibrous material." As of the application's filing date, the inventor knew of two such materials that worked successfully as conductors: carbonized paper and wood carbon. The application discloses both of these materials.

After research, the examiner has learned that there are roughly 1000 other plant species that have the relevant "vegetable fibrous material." However, only four of these species work as conductors in the claimed light bulb.

Should the examiner allow or reject the application? Please explain.