EUMYCETES— LICHENS 



307 



LICHENS 



Symbiotic organisms consisting of higher fungi, chiefly of the class Asco- 

 mycetes, or rarely Basidiomycetes ; the thallus consisting of algal cells enveloped 

 by the mycelium of the fungus forming a felted mass. The algae are called 

 gonidia and belong to the Cyanophyceae or Chlorophyceae. The reproductive 

 bodies consist of spermogonia, which contain the spermatia. The asci contain 

 the ascospores, and occur in apothecia. In the Basideal lichens, spores are 

 borne on basidia. Lichens are sometimes divided into fruticose, crustaceous, 

 and foliaceous ; but a more natural classification arranges the lichens into the 

 Basidio-Uchenes and Asco-lichenes, with various families, such as the Roccel- 

 laceae, that contains the Litmus, Roccella tinctoria ; the Lecanoraceae, contain- 

 ing the Lecanora ; and the Cladoniaceae that contains the well known Reindeer 

 Lichen, Cladonia rangiferina. 



Fig. 115. Lichens, structure of Thallus and Apothecia. 1. Plectospora mtnutula, sec- 

 tion through a part of the apothecium; a (at the right, below) Gonidia, a (above) ascus j^ 

 ascospores, p paraphyses; xSOO. 2. Section of thallus of Cladonia furcata x 330. 3. Por- 

 tion of thallus of Stereocaulon rumulosum: a gonidia, m hypha. 4. Isolated gonidium 

 (o) with attached hyphae (m) x 950. 5. Synalissa ramulosa, isolated gonidia (a) with 

 attached hypha (m). After Bornet. 



