LICHENS, GENERA AND SPECIES 



The Genus CETRARIA, (Ach.) Fries 



The Spanish-shield Lichens. The members of this genus 

 are generally found on trees, although sometimes they are found 

 on rocks or even earth. The colour on the upper surface is bright 

 yellow, greenish-yellow, straw, olive, or brown. 



The thalhis is expanded and leaf-like or shrubby (fruticulose 

 or fruticose) with branches compressed or channelled; the lobes 

 are flattened and broad; root-like growths on the under surface 

 (rhi^oids} are few or wanting. 



Fine hairs (cilia) are frequently present and sometimes are 

 numerous. 



Soredia are rare. 



The fruiting di-sks (apothecia) are medium in size or large; they 

 are attached on or near the margin of the lobes; the disk itself is 

 shield-shaped, light chestnut to dark reddish-brown. The shape 

 of the disk suggested the name Cetraria, from cetra, a Spanish 

 shield. 



The Pitted Cetraria, Cetraria lacunosa, Ach. See Plate II. 



Habitat. On trees and old fence-rails, easily detached. 



Vegetative organ (thalhis). Leaf-like (foliaceous) the lobes 

 rounded, the surface pitted (lacunose) ; pearl to slate colour above, 

 white to darker below, margins scalloped. 



Fruiting disks (apothecia). Abundant on the lobes, some- 

 what elevated, the disk light chestnut, growing darker, the 

 margin entire. 



Name. The specific name lacunosa is from the Latin lacus, 

 a saucer, referring to the pitted surface of the thallus. 



Iceland Moss, Cetraria Islandica, (L.) Ach. See Colour 

 PJate VII. 



Habit and habitat. On earth. 



Vegetative organ (thalhis). --Cartilaginous and shrubby 

 (fruticulose); usually brown above, lighter toward the base 

 where there is sometimes a red stain. 



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