Not all sources of caffeine...

[Lexicon]

in reply to My preferred source of caffeine is...

While they all contain related stimulants, coffee, tea, and chocolate's "caffeine" are all different chemicals.

Coffee contains caffeine
Tea usually contains theophylline, though I think some black teas contain true caffeine.
Chocolate contains theobromine

[Skeeve]

The German wikipedia states that Tea contains "Teein" (don't know the english term) and that it's chemicaly absolutely identical to caffeine. It also saiys that "Teein" is an outdated word...

[Lexicon]

And the english wikipedia states that tea contains theophyline. And it also says "Caffeine is sometimes called theine when it is found in tea, as the caffeine in tea was once thought to be different than the caffeine found in coffee."

This is why I don't particularly trust wikipedia. I've seen this confusion go back and forth on web sites for a while now, and my best guess for now is that some teas contain caffeine and some contain theophylline. They are undoubtedly different but related chemicals.

[Skeeve]

And the english wikipedia states that tea contains theophyline. And it also says "Caffeine is sometimes called theine when it is found in tea, as the caffeine in tea was once thought to be different than the caffeine found in coffee."

That's no contradiction. Tea simply contains both: Theine (aka. caffein) and theophyline. I just looked that up in my wife's medical lexicon and it states that teeleafs contain theophyline.

So your first statement was not quite right as tea also contains caffein.