lichen (ไลเคน)

Thai-English name for a composite organism that grows on the surfaces of trees and rocks and consists of two or more dissimilar organisms that form a symbiotic relationship to produce a new vegetative body that is called a thallus, of which the type is used to categorize a growth form. The life forms are composed of a fungus and most often a green alga and/or a cyanobacterium. The fungal filaments make up about 80% of the lichen body. They come in many forms, colours and sizes, and though they may sometimes appear plant-like, they are not plants. The growth forms are grouped in nine categories, namely: fruticose, which members grow like a tuft; foliose, which grow in flat, two-dimensional, leaf-like lobes (fig.); crustose, which are crust-like and adhere tightly to a surface; squamulose, which are formed of small leaf-like scales crustose below but free at the tips; leprose, which are powdery in appearance; gelatinous, which are jelly-like; filamentous, which members apear stringy or like matted hair; byssoid, which members are wispy, somewhat like teased wool; and a last structureless group. 回