Stone tools we’re first used around 3,300 BCE
The vascular cambium produces secondary phloem and xylem tissue.
Vascular cambium, a plant tissue located between the xylem and the phloem in the stem of a vascular plant. It is also the source of both secondary xylem growth and the secondary phloem growth. Vascular cambium is usually found on dicots and gymnosperms not on monocots which usually lack secondary growth. It does not transport water, dissolved food or minerals by plants.Vascular cambia are cylinders of unspecialized meristem cells which divide to make new cells which specialize to form secondary vascular tissues.<span> </span>
<span>When ozone forms near the ground, it is known as a secondary pollutant. This is because it is the result of two primary pollutants reacting to create a new substance. The reaction between the primary pollutants is airborne and then the resultant ozone settles near the surface of the ground.</span>
