: The evolution of the pollen tube allowed plants to reproduce without needing external water for sperm to swim through, a major leap in the colonization of land. Specialized Structures in Gymnosperms
: In more primitive seed plants like cycads, the mature pollen tube is haustorial—it grows into the nucellus tissue to absorb nutrients. Eventually, it releases motile, flagellated sperm cells into a "fertilization chamber" near the egg. mature orgasm tubes
: These are unique because their mature pollen tubes do not carry the sperm all the way to the egg. Instead, the tube functions as an anchor and nutrient-absorber, eventually bursting to release large, swimming sperm. : The evolution of the pollen tube allowed
