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.
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