sentences:  To be free from the constraints of small size and constant moisture that the parenchymatic transport system inflicted, plants needed a more efficient water transport system.As plants grew upwards, specialised water transport vascular tissues evolved, first in the form of simple hydroids of the type found in the setae of moss sporophytes.These simple elongated cells were dead and water-filled at maturity, providing a channel for water transport, but their thin, unreinforced walls would collapse under modest water tension, limiting the plant height.