Complex sentence: Once a seed lands on a branch it will germinate and grow a haustorium which penetrates past the cambium layer and into the host's xylem and phloem tissues; from those tissues it gathers nutrients needed for its own growth and reproduction.
Split into simpler sentences: Once a seed lands on a branch, it will germinate and grow a haustorium which penetrates past the cambium and into the host's xylem and phloem tissues. From those tissues it gathers nutrients needed for its own growth and reproduction.