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
Native Seeds/SEARCH grant to pursue his studies of the agronomic characteristics and health value of desert food plants, including in relation to controlling diabetes among Indians and Hispanic Americans. As of 2016, the Native Seeds/SEARCH seed bank contained seeds from over 1800 plant varieties. In addition to a seed bank, Native Seeds/SEARCH opened a conservation farm in 1997. Seeds are distributed by mail order and a retail store in Tucson. Since 2001, Native Seeds/SEARCH has operated Southwest Regis-Tree to conserve Native Southwestern perennial species. Native Seeds/SEARCH Native Seeds/SEARCH, founded in 1983, is a nonprofit conservation organization located in Tucson, Arizona in the