Question

describe the types of lichens on the basis of their thallus organisation

Answer 1

Hey..mate here is yur ans...
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$\textbf{CRUSTOSE}$
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The size of the thallus of crustose is insignificant. The body of crustose is flat, thin and it is usually without any distinct lobes. Their body is just like a thin layer. Scientists Gave them Name $\textbf{Crustose}$beacuse on thier body crust is present and it is closely attached by the whole of its lower surface like stones or rocks, bark and similar hard substrata.Generally it is too hard we can't break it easily. The surface of the thallus is usually divided into more or less hexagonal areas and we called the areas as areolae. In many species, the thallus is partly buried in the substratum.
Eg :-➡$\textbf{HEMATOMMA PUNICIUM}$
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2)$\textbf{FOLILOSE}$
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The Thallus of $\textbf{Folilose}$ is more striking. The are flat, broad, much lobed and it is also look like a leaf. They appears crinkled and twisted leaves. They have a distinct upper and a lower surface. The lower surface may be looks white or sooty.The edges Of Leaves are usually curled up. Their Thallus is attached To Rocks and Rhizoid like outgrowth called Rhizinae. And $\textbf{Question}$⤵⤵⤵⤵
$\textbf{What is Rhizinae??}$
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$\textbf{Answer}$
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Rhizinae arise from its lower surface. In some foliose lichens, the rhizine consists of a single, simple to branched hypha.They are dark or dark brown in colour. The thallus, in some species, is attached to their substratum by a single rhizine. It grows from the centre of the lower surface of the thallus.In others, the thallus is attached by Many rhizines.
Eg➡Xanthoria, Physcia, Peltigera, Parmelia, Cetraria and Cluiudhuria.
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3)$\textbf{FRUTICOSE}$
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Fruticose are the most conspicuous and Fruticose have a most complex thallus which is slender and freely branched. Their branches may be cylindrical or ribbon-like (flattened) and form thread-like or twig-like tufts. In many species of Cladonia, their branches are stand stiffy erect making the thallus resemble a tiny bud. They have other(Usnea) in which the branches are pendant (hanging) and tassel-like. The thallus is attached only at the base by a flattened disc.The fruticose lichens make extensive and attractive growths standing out from the rocks, foliage and branches of trees. The thallus shows no differentiation into upper and lower surfaces.
Eg➡$\textbf{Usnea, Cladonia and Ramalina}$
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4)$\textbf{SUQAMULOSE}$
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The thallus of Squamulose is scale-like and composed of small lobes.
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Answer 2

The different kinds of lichens on the basis of thallus organization are:  

1. Crustose lichen: It exhibits leaf-like thalli and colonizes the rocks after foliose lichen. They assist in captivating more water, and thus enhances the moisture content of the soil. For example, Graphic scripta.  

2. Foliose lichen: It exhibits flat thallus with leaf-like lobes comprising distinct layers of tissues. They colonize the bare surface of the rocks initially at the time of succession. For example, Parmella.  

3. Fructiose lichen: They exhibit the most composite thallus, that is, cylindrical, branched, and at certain times hangs like a tassel. They are witnessed on the branches of the tree on the rocks. For example, Usnea.