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
Burpee Seeds the previous year as one of six gardeners nationwide whose marigolds came closest to being white. Vonk kept seeds from the lightest flowers in her garden each season, replanting for over two decades before achieving a pure white marigold that measured 2.5 inches in diameter. Her entry in the 1975 edition of the contest topped 8,200 other entrants and produced what was then described as the "costliest flower ever." Burpee Seeds Burpee Seeds, officially W. Atlee Burpee & Co., is a seed company that was founded by Washington Atlee Burpee in 1876. The company is not named after a relationship