What is the tallest trees can grow in the Jungle Biome?
According to Wikipedia there is no real limit found in the code with regard to the height cap. There is however a limit found in the number of logs of which a tree may exist of: 55.
I've grown ones that are 31 in height, from ground to the top of their leaves. I doubt that's a maximum though.
As for a minimum, you could get at that by trying to grow trees under platforms of different heights.