Evolutionary history of plants phloem on the outside. Since xylem cells comprise dead, lignified tissue, subsequent rings of xylem are added to those already present, forming wood. The first plants to develop secondary growth and a woody habit, were apparently the ferns, and as early as the Middle Devonian one species, "Wattieza", had already reached heights of 8 m and a tree-like habit. Other clades did not take long to develop a tree-like stature. The Late Devonian "Archaeopteris", a precursor to gymnosperms which evolved from the trimerophytes, reached 30 m in height. The progymnosperms were the first plants to develop true wood, grown from
Sub Pop Seattle, he wrote a column for local newspaper "The Rocket" titled "Sub Pop U.S.A.", a column he ended in 1988. In 1986, Pavitt released the first Sub Pop LP, the compilation "Sub Pop 100", which featured material by artists including Sonic Youth, Naked Raygun, Wipers, and Scratch Acid. Seattle group Green River chose to record their "Dry as a Bone" EP for Pavitt's new label in June 1986; Pavitt couldn't afford to release it until the following year. When finally released, "Dry as a Bone" was promoted by Sub Pop as "ultra-loose grunge that destroyed the morals of a generation".