• R. Kenneth Horst
Reference work entry


A lichen is a fungus body, usually one of the Ascomycetes with apothecia, enclosing a green or blue-green alga. The fungus receives some food from the alga and the alga some food and protection from the fungus, a relationship termed symbiotic. Lichens frequently grow on living trees and shrubs, but their injury is indirect, an interference with light or gas exchange to stems or foliage, rather than from penetration of living cells of the suscept plant. There are three types associated with plants: crustose, a crust closely appressed to bark of main trunk or larger limbs; foliose, leaflike, prostrate but not so firmly attached to the substratum; and fructicose, bushlike, erect or hanging.


Living Cell Plant Pathology Living Tree Plant Health Main Trunk 
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Copyright information

© Springer Science+Business Media Dordrecht 2013

Authors and Affiliations

  • R. Kenneth Horst
    • 1
  1. 1.Department of Plant Pathology and Plant-Microbe BiologyCornell UniversityIthacaUSA

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