Glowcaps are glowing mushrooms added by the Wild Caves 3 mod. They emit fair amounts of light and come in four sizes; small, medium, normal and large, which is as big as a player.
Variants
(Please add details if there is another glowcap color.)
Glowcaps come in 2 different colors, green, by default, which is in most caves, and blue, which is only found in ice caves.
Tags
If you were looking to place this in Creative (which you can), here are some tags:
green mushroom, tall mushroom, mushroom, blue mushroom, wierd mushroom