Yes, Gentian is a plant (or, rather, a family of flowering plants).
Gentian Violet is NOT an extract from that plant, however.
Gentian violet (crystal violet, Methyl Violet 10B, hexamethyl pararosaniline chloride) is an antifungal agent, the primary agent used in the Gram stain test, perhaps the single most important bacterial identification test in use today, and it is also used by hospitals for the treatment of serious heat burns and other injuries to the skin and gums. Typically prepared as a weak (e.g. 1%) solution in water, it is painted on skin or gums to treat or prevent fungal infections. Gentian violet does not require a doctor's prescription (in the US), but is not easily found in drug stores. Tampons treated with gentian violet are sometimes used for vaginal applications.
Gentian violet is also known as Andergon, Aniline violet, Axuris, Badil, Basic Violet 3, Brilliant Violet 58, Gentiaverm, Hexamethyl-p-rosaniline chloride, Meroxylan, Meroxyl, Methylrosalinide chloride, Methyl Violet 10BNS, Pyoktanin, Vianin, Viocid, and Viola Crystallina.http://en.wikipedia.org/wiki/Gentian_violet