From Bulbapedia, the community-driven Pokémon encyclopedia.
Gloom can evolve into either Vileplume or Bellossom through different methods.
This is a list of Pokémon which evolve differently depending on certain conditions. To date, no Pokémon that evolves by branch evolution undergoes a further branch in its evolution, while no Pokémon evolves further after the branch besides Wurmple.
Most Pokémon that evolve through branch evolution do so in their basic forms, and do not make it to a second evolution. There are a few exceptions, though. Many also face this branch in a generation later than when the Pokémon is originally introduced, such as Kirlia which was introduced in Generation III along with its evolution Gardevoir, and whose second evolution, Gallade, was introduced in Generation IV.
Pokémon that evolve through branch evolution