Over time, vascular plants have evolved to adapt to new and changing environments, and one of these is the development of secondary growth. Secondary growth is defined as the increase in diameter of stems, roots or branches. This growth was most likely developed and evolved due to an increasing demand for sunlight in the lateral meristems of dicots and some gymnosperms. The cork cambia is one of two lateral meristems that makes up the periderm along with the cork and phylloderm in the stems. The periderm acts like the epidermis in terms of a multi-layered secondary protective tissue for plants. In addition to the protective aspect, cork cambia also has many uses nowadays. The cork cambia is a unique structure in vascular plants that has changed over the years and learned to adapt to the environment based on different species. This adaptation of the cork cambia is important for vascular plants, but might sometimes be obscured by the secondary growth vascular cambia. Secondary growth increases the girth of plants and was first spotted in a type of fern during the Devonian period. This type of growth was developed to compete with other plants during the Devonian period in order to obtain more sunlight for photosynthesis and for the dispersal of spores or seeds (Rachel 2010). To compete with other plants, it must reach a new height and be flexible with the help of thicker stems, roots or branches. This type of growth occurs only in dicots and in some gymnosperms in vascular plants that are not found in monocots (Secondary Growth 2009). Two lateral meristems are involved in secondary growth: the cork cambia and the vascular cambia. Meristems are a type of tissue made up of meristem cells......middle of paper......forms cork forms Cambium and cork cells in the stem of Pelargonium hortorum Bailey. Bulletin of the Torrey Botanical Club. 79(4): 312-328. Frank GL. 1955. The origin and development of Cambium cork cells in the stem of Pelargonium hortorum Bailey. American Journal of Botany. 42(10): 929-936. Rachel S., Andrew G. 2010. Developmental evolution of vascular change and secondary growth. New phytologist. 186(3): 577-592. Ray FE., Susan EE. 2013. Crow Biology of Plants. 8th ed. New York: W. H. Freeman and Company. P. 391-429.Secondary growth [Internet].: General Botany; [updated January 22, 2009; cited December 10, 2013]. Available from: http://people.eku.edu/clarkro/secondarygrowth.htmThomas LR. Secondary growth in roots [Internet]. California: Tomato Anatomy; [updated 1996; cited December 10, 2013]. Available from: http://www-plb.ucdavis.edu/labs/rost/tomato/roots/secondary.html