Vascular Cambium

The vascular cambium is the lateral meristem responsible for producing all of a dicot stem's secondary vascular tissue - secondary xylem (wood) laid down toward the inside of the ring and secondary phloem (bast) laid down toward the outside. Unlike a textbook meristem, an active vascular cambium does not consist of small, densely cytoplasmic, isodiametric cells; instead its cells develop a large central vacuole (or several vacuoles) surrounded by only a thin layer of dense cytoplasm, an adaptation that lets the cambial ring expand in circumference as the stem it surrounds keeps getting thicker. Structurally, the vascular cambium is built of two distinct kinds of initials working together - vertically elongated fusiform initials, which produce the plant's long-axis (axial) conducting and supporting cells, and horizontally elongated ray initials, which produce the short, radially-oriented ray cells that carry materials sideways across the wood and bast. How t …