where does water enter the vascular system of a starfish
Water vascular system In sea stars, water enters the system through a sieve-like structure on the upper surface of the animal, called the madreporite. This overlies a small sac, or ampulla, connected to a duct termed the stone canal, which is, as its name implies, commonly lined with calcareous material. The stone canal runs to a circular ring canal, from which radial canals run outwards along the ambulacral grooves. Each arm of a sea star has one such groove on its underside, while, in sea urchins, they run along the outside of the body.[11]:933â€“939
Vascular cambium Other names for the vascular cambium are the main cambium, wood cambium, or bifacial cambium. In more detail, the vascular cambium is a plant tissue located between the xylem and the phloem in the stems and roots of certain vascular plants.[1]:125 It is a cylinder of unspecialized meristem cells that divide to form secondary vascular tissues. It is the source of both secondary xylem growth inwards towards the pith,[2] and secondary phloem growth outwards to the bark. Unlike the xylem and phloem, it does not transport water, minerals or food through the plant.[2]