Drag the terms on the left to the appropriate blanks on the right to complete the sentences. Terms may be used once, more than once, or not at all.
1. Secondary growth produced by the is unidirectional due to cells being added only to the outside of the cambium layer.
2. Secondary growth produced by the is bidirectional due to cells being added to both sides of the cambium layer.
3. The vascular cambium generates to the inside and to the outside.
4. The majority of cells added during secondary growth are .
5. The tissue that is commonly referred to as "wood" in a woody plant is composed of formed from the vascular cambium.

In plants, growth is characterized by the elongation of the stem and roots. Woody plants also gradually increase is girth throughout their life times. Plant growth is divided into two types depending upon the two growth dimensions (height and width):

Primary Growth:

The elongation or increase in the lengths of the stem and roots is termed as primary growth. Primary growth occurs due to the rapid cell division at the shoot and root apical meristems. This rapid growth of the apical buds is called apical dominance and it prevents the development of lateral buds.

Secondary Growth:

Secondary growth is the increase in the thickness or width of the plant. This occurs due to the growth of lateral meristems i.e. the vascular cambium and cork cambium (in woody plants). Stem thickening occurs through the division of the vascular cambium located outside of the primary xylem and inside of the primary phloem. This division leads to the formation of the secondary xylem and phloem. The cells of the secondary xylem contain lignin and form the "woody" portion of the plant.

In woody plants, the cork cambium is the outermost lateral meristem and produces cork cells that provide strength and hardiness.