Vascular cambium

The vascular cambium is a lateral meristem.

It is the source of both the secondary xylem (inwards, towards the pith) and the secondary phloem (outwards), and is between these tissues in the stem and root. Only a few leaves even have a vascular cambium.^[1]

Vascular cambium is a type of meristem - a tissue consisting of embryonic (not specialized) cells which can produce other (and more differentiated) plant tissues originate. Primary meristems are the apical meristems on root tips and shoot tips. Another lateral meristem is the cork cambium, which produces cork, part of the bark.

1. ↑ Ewers, F.W. 1982. Secondary growth in needle leaves of Pinus longaeva (bristlecone pine) and other conifers: Quantitative data. American Journal of Botany 69: 1552-1559. https://www.jstor.org/stable/2442909