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
Seeds of Diversity and daughter of W. Garfield Weston, launched through the W. Garfield Weston Foundation, a program to be administered by USC Canada and Seeds of Diversity. The aim of the program is to work with regional partners to "build a more secure and diverse ‘made-in-Canada’ seed supply" by promoting the production and use of locally adapted and diverse seed for crop plants. Seeds of Diversity Seed of Diversity, Semences du patrimoine, is a Canadian charitable organization that aims to "search out, preserve, perpetuate, study, and encourage the cultivation of heirloom and endangered varieties of food crops", particularly Canadian plants, and to