bark

Bark is the colloquial term for the protective outer layer of tissue on woody plants such as trees and shrubs. The technical name for bark is vascular cambium. Depending upon the species of plant it belongs to, bark can be very specialized. It can be thick, thin, smooth, scaly, or adapted to withstand fire. Some bark, like that of palo verde trees, is infused with chlorophyll and is able to produce food directly from the sun, just like leaves.