As far as I understand, "dry herbs" cannot be used in an e-cig, because they don't operate under the same conventions of burning as do normal cigarettes - so they herbs wouldn't be broken down and vaporised.
BUT.. If you do want to use certain herbs in e-cigs, then you can enjoy them by creating an oil out of the herb product.
For example, stoners have been using hash oil or thc oil, and that smokes in e-cigs, usually with only minimal modifying - and has provides hits of up to 90% THC.
Here are a couple of videos I'd suggest you check out if that is your thing: