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
Lapeirousia lobes may be subequal and spreading, or unequal with upper largest petals erect, the lower three forming a lip. The stamens are symmetrically arranged. The fruit is a membranous capsule containing many small seeds, either globose or angled by pressure. Some forty species have been described from sub-Saharan Africa, of which about a third are endemic to fynbos. Common names are various and regional, including "painted petals", "cabong", "chabi", "" (Afrikaans for "wheat flower"). The flowers are commonly scented, though possibly only at certain times of day. The plants are of considerable biological and evolutionary interest because of their adaptions