What on earth...? I mocked a similar inquiry, perhaps even from the same person, saying "You want to know where you can defeat a Chikorita?" YES. Yes this guy does. With a little investigation, it turns out that you cannot have Chikorita in your National Dex if you choose Cyndaquil. Yet even that cannot save the steaming turd that is this question. Ask a friend if they'll give you an egg that will hatch into one. Or, if you have no friends, ask the GTS for a Bayleef or Meganium, which are in your National Dex, and breed that on your own. Just accept this as a side-effect of a game that tries its best to encourage trading. Speaking of which, Chikorita is on Professor Elm's desk the whole time. He couldn't simply, you know, slip you a peek so you can obtain data for his own Pokedex? Yeah, screw you, Gamefreak.
a411 You must trade to have Chikorita in your National Dex.