The complete Pokemon RBY pokedex, part 5

Pokémon Name: Vileplume
Type: Grass/Poison
Classification: Flower Pokemon
Pokédex Number: 045
Ability: Chlorophyll
Dream World ability: Effect Spore
Useful Attacks: Solarbeam
Location Found:
D/P/P/HG/SS: Evolve from Gloom
B/W: Evolve Gloom

There are two reasons why Vileplume is better than Gloom. One, it learns Solarbeam, and two, it lacks Gloom's toe-curling stench. An all around solid Pokemon to have when you're looking to poison, paralyze or leech an opponent.

Evolution: From Gloom via Leaf Stone