cambium

American Heritage® Dictionary of the English Language, Fourth Edition

1. n. A lateral meristem in vascular plants, including the vascular cambium and cork cambium, that forms parallel rows of cells resulting in secondary tissues.

Century Dictionary and Cyclopedia

1. n. In civil law, exchange; the exchange of lands, money, or evidences of debt.
2. n. In botany, a layer of tissue formed between the wood and the bark of exogenous plants. It was believed by the older botanists to be a mucilaginous fluid exuded between the wood and the bark, and organized into new wood and new bark. It is now known to be not a fluid, but a layer of extremely delicate thin-walled cells, filled with protoplasm and organizable nutrient matter, and appearing like a thin film of mucilage. These cells develop on the one side into a layer of new wood, and on the other of new bark, while at the same time fresh cambium is formed for the continuation of the work. It is by the renewal of this process year after year that the increase of growth in the stem is effected, as indicated by its concentric rings. In the primary fibrovascular bundles of the stem a similar layer of cambium, with the same function, is always found between the woody and cribrose portions.
3. n. A name formerly given to a fancied nutritious humor which was supposed to repair the materials which the body is composed.

Wiktionary

1. n. botany A layer of cells between the xylem and the phloem that is responsible for the secondary growth of roots and stems.
2. n. obsolete One of the humours formerly believed to nourish the bodily organs.

GNU Webster's 1913

1. n. (Bot.) A series of formative cells lying outside of the wood proper and inside of the inner bark. The growth of new wood takes place in the cambium, which is very soft.
2. n. (Med.) A fancied nutritive juice, formerly supposed to originate in the blood, to repair losses of the system, and to promote its increase.

WordNet 3.0

1. n. a formative one-cell layer of tissue between xylem and phloem in most vascular plants that is responsible for secondary growth
2. n. the inner layer of the periosteum