FRUTICOSE LICHENS ​

STUDY OF EXTERNAL FEATURES OF THALLUS (FRUTICOSE LICHENS)

Comments :-

  • These appear shrubby with cylindrical, flat or ribbon-like body.
  • It is upright, generally branched and pendulous. 
  • It remains attached to the substratum by rhizoidlike structures forming a disc.
  • The common examples include Usnea, Alectonia, Cladonia, etc.

FRUTICOSE LICHENS ​


FRUTICOSE LICHENS ​

STUDY OF INTERNAL STRUCTURE​ OF THALLUS (FRUTICOSE LICHENS)

Comments :-

  • The transverse section appears almost circular. 
  • The internal structure shows four distinct regions, outermost cortex, the algal zone, medulla and the centrally located chondroid axis. 
  • Thallus structure is radially symmetrical. 
  • The cortex is made of closely packed and interwoven fungal hyphae. Intercellular spaces are absent.
  • The algal zone consists of cell of unicellular green alga, Protococcus. 
  • Medulla follows the algal zone. It. consists of algal cells loosely mixed with fungal hyphae scattered in different directions.
  • The central chondroid axis is made of longitudinally arranged, compact, thick walled and closely grouped fungal hyphae.

FRUTICOSE LICHENS ​

STUDY OF VEGETATIVE STRUCTURES OF FRUTICOSE LICHENS ​

Comments :-

  • Vegetative propagation takes place by fragmentation, isidia and soredia.
  • Fragmentation is the commonest of all the methods. 
  • Isidia develop as outgrowths of thallus. These develop into new lichen thalli after separating from the parent thallus. 
  • Soredia are bud-like outgrowths developing either from the entire surface or in localised patches called soredia. 
  • Soredia are developed in the gonidial layer.
  • A soredium consists of a few algal cells surrounded by hyphae.
  • Soredia get detached from the thallus and are carried away by the wind. Germination occurs on suitable substratum.

FRUTICOSE LICHENS ​

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