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
Sub-district VII of Warsaw suburbs (of Armia Krajowa) for advancing soldiers of the 27th Wołyń Division of Armia Krajowa. In September, medical aid was provided for insurgents of the "Kryska group", who succeeded in swimming across Wisła from the Czerniaków bridge-head to the Praga bank of Wisła river. Region V - it covered the Chojnowo forests, which were a place of concentration of the sub-district's units as well as units of the Sub-district IV of Ochota (of Armia Krajowa) and Sub-district V of Mokotów, which failed to perform their military action on their own area. The commander of the Sub-district IV of Ochota lieutenant-colonel Mieczysław Sokołowski pseudonym "Grzymała",