These exterior layers have many specializations that are nicely covered in your book. Ground tissue fills the space between the dermal tissue and the vascular tissues. But it is more than filler. As I mentioned before, this is where virtually all of the interesting biochemistry goes on. This is where virtually all of the photosynthesis occurs, for example.
Vascular tissue is a conducting tissue type.
The flow of water from soil to atmosphere along this xylem pathway is called transpiration . Phloem is a specialized parenchyma tissue. The phloem cells have a cytoplasm and are therefore alive. The conducting cells have at least a rudimentary metabolism. They depend on adjacent companion cells for most of the directed metabolism and supply of essential raw materials for life.