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 become prone to colony collapse disorder, which threatens the production of many insect-pollinated crops. Native bees are also in decline, which is partly due to loss of nesting sites in plant debris and in open untilled ground, and partly due to reduced diversity of food plants. Seeds of Diversity initiated a project called Pollination Canada with the aim of increasing awareness of native bees and alternative pollinating insects in order to protect them, so that farmers and urban gardeners can decrease their dependence on honey bees. Pollination Canada has 28 other partner organizations. In February 2013, Gretchen Bauta, Canadian philanthropist